I think it all depends on the size of the venue and how often you play gigs as well as the percentage of time you spend onstage with the acoustic guitar..... and of course, how much discretionary income you have to spend on amps.
 
I've played acoustic with both sound hole pickups and Pizeo pickups through my normal guitar amp as well as into the PA.  Most amps have the ability to be set and played very clean. Even the Marshall can be set to a crystal setting. If you're playing a few songs out of the entire night, on the acoustic, this should work relatively well. Not putting down the audience, but a hard rocking audience isn't going to complain about you using a Marshall for an acoustic tune or two.
 
If on the other hand, you are playing a substantial amount of acoustic guitar in the average nightly set, you will certainly want to invest in the proper gear. The reason I could see for using a stage amp would simply be to hear myself properly. Going direct relies on the FOH mixer and the stage monitor mixer (if you have one) to set the proper levels for the performers to hear properly.

Rain
...
As for Brahms - it's funny because I love to play rock and metal and I am involved in a couple of bands right now. But outside of that, and except when working out in the gym, I seem to gravitate towards classical music pretty much exclusively these days - there's just so much stuff that I'm only discovering, so many great works to listen to.
...

And you will find even more by the time you start listening to things you know conducted by someone else. It's a treat. And very different on the accents and definition of the orchestra, as well as its positioning to provide different emphasis on various details. This was used to magnificent effect by Bernard Herrmann who did all of those science fiction films and Hitchcock as well in the 50's and 60's.

From a technical approach I think it's necessary. From the opinions expressed so far it isn't absolutely necessary to some. 
 
With a dedicated acoustic amp I think you get a better sound. They are designed for the kinds of pickups in acoustic guitars with regard to impedance. Strictly speaking they aren't all mini PAs. Some of them have special efx and filters designed for acoustic guitars only. The whole purpose being to hopefully make the sound you already have louder without color . If the goal is to add color, then you might have a different opinion. Electric guitar amps were obviously designed for electric guitars. Probably more times than not players recruit electric guitar amps for the purpose and roll with the differences.
 
If I had a nice Martin or Taylor and didn't want it to sound any different, I would be looking at acoustic amps. In the case of using a PA input instead, most acoustic guitarists who play regularly use high quality dedicated DI boxes instead of those cheap boxes. You're still at the mercy of the sound guy though.
 
An acoustic amp could be dual purpose.If you have something like a Line 6 POD it might actually sound better through the line inputs of an acoustic amp. From everything I read they work best on an amp with the flattest freq. possible...that would be a good PA, keyboard amp, or an acoustic amp. Not an electric guitar amp because they don't have a flat frequency response.
 
I've never yet really heard an acoustic sound very good through an amp if it wasn't made for it. I'm picky though.

Hi,
 
Honestly, I think you guys are getting way too picky and silly. 90% of the audience can not appreciate the music to the level that you think, and being critical about the last 5 to 10 percent is weird ... almost no one in the audience will know, or understand the difference.
 
I will say, though, that the right combination at the right time, usually makes a difference between good and bad, but I doubt that a different amp is the reason why ... I think the person crystalizing their experience and mix/match the amp/acoustic together is much more important than just a mere idea that a better amp or mike, will make this guitar sound better when it isn't that good.
 
Every instrument, including a kid's play guitar has its place and it can be used ... anywhere ... if done right!
 
I say concentrate more on your material and improve it ... and that thinking that only a monster amp can save your bad voice, is bizarre.  This was one of the main reason why I did so well with new actors and actresses, because they did not have any "ideas" about anything, except how to learn their lines and play them to the best of their ability. And that made for a much fresher presentation, than the one that would otherwise be more slick ... and have nothing to show for it. This was the difference, for me, in seeing Mississipi Charles Bevel with Chick Streetman on plain guitar and no amps, and David Crosby solo with an amp, and sounding horrible. And the other 2 guys could sing around David, not that he was a bum on that score. He was good, but on that night, he got taken to school!

"Honestly, I think you guys are getting way too picky and silly. 90% of the audience can not appreciate the music to the level that you think, and being critical about the last 5 to 10 percent is weird ... almost no one in the audience will know, or understand the difference."
 
This is Rain's post, so I won't take it off base, but to answer your comment. For myself, it isn't about what the audience can notice. It's about what I like to hear.

Starise
This is Rain's post, so I won't take it off base, but to answer your comment. For myself, it isn't about what the audience can notice. It's about what I like to hear.

Understood ... however, you are more critical about it all, than the audience can see or hear. From a directing perspective, an amp can not make your guitar and hand/voice sound better ... and on any given day, you might sound better than the best without all that stuff ... I'm not sure you can see this, since we live in a consumerist society that thinks there is always better out there, and in your case or mine, our voice and hand is not it!
 
Weird is all I can say! Concentrate on YOUR OWN magic ... not what the amp can do or not. Regardless of amp, your magic will come across just fine, because it can not be removed! Magic is magic ... an amp is just an amp ... supposedly adding more to your magic ... and that is a bit of a rock music fallacy about louder is supposedly better and cleaner.
 
I've told Rain this before in different posts. He knows it, but won't discuss it, and instead is looking for other things, that are not within him and his wife for the music they want to create. The magic will not be on any amp. PERIOD! The magic is WITHIN! Even in Las Vegas!
 

Right.  See, Pedro, ol pal...some of us do this for US...not for them;-)
 

As you can see from my "for sale" pics, the Blonde can handle two (and even three!) inputs with an included aural enhancer (plus the tuner out is a nice addition).  She's quite the slut isn't she? 
 

Turn her around and you find an effects loop, level adjustments, a reverb return and footswitch jack as well as outputs to the board.
 
In other words, pretty much everything you might need for two people to play an acoustic set, be able to hear themselves while sending a signal to the FOH.

I think you make some valid point's Strarise ,
 
Somebody that is geared up as an acoustic instrumentalist or a multi instrumentalist where they double on various stringed acoustic instruments would probably be best served by a dedicated acoustic amplification rig .
For those that have made the investment to go there they did so with their eyes wide open ...
 
Personally I have nothing against an amp made specifically for acoustic instruments .. I would not want it to be my only amp  ...
There's a lot of ways to skin that cat ...
I had a JC 120 for a while and I never even plug ed into the front end ..
I used to run stereo through a rack mount pre amp and effects chain and bypass the whole JC 120's  preamp section all together .....That amp had 2 inputs in the back for plugging in and running a different signal chain  .
Just about the same can be done with any amp that has a send return ...
Just plug into the return section  w  a preamp or a pod ...
A lot of the new S S or hybrid amps come with an auxiliary input so people can play along w a CD ...
A person that knows what they are doing can feed the auxiliary input  w a nice little mid to high level Acoustic Guitar Specific Pre amp ...
Heck even those can be costly for a name brand high quality unit ...Yet they do offer the advantage of portability and studio quality sound ...
Speaking of studio quality sound for an acoustic guitar that is consistent , reliable , portable  .
This one goes out to Rain...
I know you have a Mackbook Pro 13 w Logic ...have you ever dialed up an acoustic dream guitar sound and ran it through your powered home studio monitors ?
If you like the way that sounds you may not even need an acoustic guitar amp ..you may only need a small self powered stage monitor 
 
just a thought ,
 
Kenny
 

Oh I love those old JC 120's. I would have had one if my studio was bigger. Two 12" speakers even at half volume are a bit much in a bedroom setting...probably lift the shirt right off my behind. Like running from a lit M-80
 
If price wasn't an issue I would have one of those Bose "stalk" systems for live playing. Hard to beat one of those, even with a stick. I won't ever have one though because I only play sessions in small bars with 4 to 6 other players. The patrons want you loud but not so loud they can't talk to one another.You can hear all you need to hear in there without amplification.