Versus using a regular amp I mean. 
 
I'm not a fan of acoustic electric sound - it seems so backward to me to capture the sound under the strings. But it has its use and I've come to terms with the idea. 
 
I would assume that if there's a P.A. involved, the preferred method would be to go direct into that, anyway. So unless you find yourself in a situation where you have to play live w/o a  P.A. but to be loud enough for a big room, there's no point in using an amp at all. 
 
But in such a scenario, would it make that much of a difference to have a dedicated acoustic amp instead of using one I already own? Do people get as anal about acoustic amps as they do over electric amps, you know, tube vs solid state and all?
 
I've been an electric guitar guy for 30 years or so, and acoustic is a whole new paradigm to me...

Depends what you're trying to do.  I used to have an SWR California Blonde that I mostly used at home but, when my friends came up here to play in a casino, they were pretty excited to have it available.  I've always assumed it's because it has been set up to amplify as cleanly as possible and any extra abilities were specifically to make an amplified acoustic tone sound better.  Naturally, most amps meant for electric guitar contribute (i.e., color) the tone hopefully in a musically pleasing manner.
 
(BTW - Brahms says that he prefers an acoustic amp.)

craigb
Depends what you're trying to do.  I used to have an SWR California Blonde that I mostly used at home but, when my friends came up here to play in a casino, they were pretty excited to have it available.  I've always assumed it's because it has been set up to amplify as cleanly as possible and any extra abilities were specifically to make an amplified acoustic tone sound better.  Naturally, most amps meant for electric guitar contribute (i.e., color) the tone hopefully in a musically pleasing manner.
 
(BTW - Brahms says that he prefers an acoustic amp.)

 
Makes sense. :)
 
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.
 
It's also much easier to read while listening to Schubert than it is listening to Cradle of Filth. 
 
I don't know. At the risk of sounding pedantic or overly dramatic, I feel like I've made decent provisions of popular music and medias in my life time, and being in my 4th decade, I somehow feel the need to use what little time I have left more discerningly. 

Nothing shocking to me!  I've got over 100 really high quality Classical CD's.  At one point, I had more Mozart CD's than any other band or artist (not really close any more - hard to compete with over 160 Tangerine Dream albums - lol!).

craigb
Nothing shocking to me!  I've got over 100 really high quality Classical CD's.  At one point, I had more Mozart CD's than any other band or artist (not really close any more - hard to compete with over 160 Tangerine Dream albums - lol!).

These days I seem to be collecting Requiems and Masses and sacred music. Tomàs Lui de Victoria's Requiem has been a huge hit with me.
 
I've only just discovered Penderecki and his Polish Requiem last week - though I'm usually not that into more modern orchestral music and seem to have a preference for music before 1850-ish, that's one that I really, really like.

I had an Acoustisonic Jr years ago.  Great sounding amp.  Not true of an A/E played into a regular electric guitar amp.  A lot of the acoustic amps are actually mini PAs with handles that have features that make them handy for a solo artist or duo and for A/E guitars specifically.  For example, the Acoustisonic Jr had a notch filter that all but killed pick attack noise.  It also had a nice chorus and reverb.  Add the 2nd inst/mic channel and it was all a duo needed.
 
I like using small amps when I play acoustic to get a touch of reverb and/or chorus and to get some sound pointed back toward me.  If I'm not recording, I mostly use my THR10 ACO setting for my A/E.  Very sweet to me.  If I am recording, I go straight into my interface.
 
The reason I no longer have the Acoustisonic is b/c I NEVER play out.
 
 

Acoustic amps are nice but limited in terms of venue size. If the venue is real big you would have to mic it to the P.A.
 
Your Marshall is really not suited to acoustic work. My suggestion would be a good quality pre amp made for acoustic feeding the P.A. and in smaller venues just use a mic.
 
I'm sure others with more experience would chime in. Most of the players I work with are using microphones because they don't care for the sound of a piezo pickup.

Had the Cali Blonde for years. Great acoustic amp. Replaced it with the Strawberry Blonde a couple of years ago. Much lighter:-)

Rain

craigb
Nothing shocking to me!  I've got over 100 really high quality Classical CD's.  At one point, I had more Mozart CD's than any other band or artist (not really close any more - hard to compete with over 160 Tangerine Dream albums - lol!).

These days I seem to be collecting Requiems and Masses and sacred music. Tomàs Lui de Victoria's Requiem has been a huge hit with me.
 
I've only just discovered Penderecki and his Polish Requiem last week - though I'm usually not that into more modern orchestral music and seem to have a preference for music before 1850-ish, that's one that I really, really like.

I was the same way with Renaissance guitar and lute music at one point. Was totally obsessed with the music of John Dowland, Anthony Holborne and Francesco Da Milano. To me there is something fundamentally beautiful about the music of that era and those guys were absolute masters of it. My CD shelf is bursting with that kind of music and I also have most of it in standard notation, used to play it obsessively on guitar (with the G string tuned to F#, natch). 
 
Regarding acoustic guitar amps, I've always been of the opinion that the only reason you would amplify an acoustic guitar with a pickup would be for convenience sake. The raw acoustic sound or the miked sound is always better, to my ears anyway. Bert Jansch in the latter part of his career played an electro-acoustic Yamaha live and I was not a fan of the sound, at least not compared to the beautiful miked guitar sound on his albums. 

FWIW , I'm basing my opinion on playing out in clubs , not arenas ...
 
The times I have played out and not mic'ed my acoustic guitar were the times where I used a sound hole pickup .
I happen to like the way that sounds over a peizo pick up if there is no sound system and mic available and I found it totally unnecessary to use an amp designed for acoustic guitars ....
My personal preference when I have played out is to use on of my Fender combo 's ...
I have used my 1966 Fender Vibrolux Reverb for electric and acoustic gigs and have gotten great results ...
Same thing goes for some other Fender combo's I have ...Super Champ , Champ ....
 
Honestly I do not see the point of getting an acoustic guitar amp unless some one is looking to run a mic + an an acoustic guitar at the same time and mimic what a small portable PA would sound like ...
That is unless some one wants to use it as a personal on stage monitor and run a direct out ...which many of the acoustic guitar amps have ...
 
If you are hard up for cash and you want to make due ,+ you don't need to run a mic at the same time into the amp you want to use for your acoustic I would recommend a variety of different amps ...
 
I have used a Vox Pathfinder 15 R for acoustic guitar in small clubs un mick'd  and have had very satisfying results It has filled the room and places where people were out to listen to music
It is good enough for Nora Jones   it's good enough for me ....about a hundred bucks or less used ...
 
Additionally there are  plenty of affordable choices out there .
Roland cubes work good for acoustic guitar , Solid State Fender combo's ...heck the 2 input combos with two speakers run low 2's  used ...even new they are cheap ...
A 2 input amp means you can run a mic in addition to your acoustic ...
Peavey Keyboard and Bass amps are decent ..actually any  2 input S.S guitar combo's would fit the bill ..if you need to add a mic w your acoustic ...
The Fender Excelsior is set up for a guitar and Mic combination , nice tube amp ...about 3 bills ...
I can go on and on
I have had people that have brought acoustic guitar amps to clubs ask me if it was OK to use my amp for their second set
 
Kenny