Recording acoustic guitar - small diaphragm condenser that much better?

As a disclaimer, I'm still a complete newbie at recording acoustic guitar. I seem to spend most of my time "in the box" messing with synths, which is a shame since acoustic guitar has been my forte since forever. So now I'm trying to incorporate it into my tunes a lot more. 
 
My only mic (apart from the one you get with ARC2) is a AKG Perception 220, a large diaphragm condenser. I think it cost me around $150 - a pretty good deal because to be honest I've been blown away by its quality. Recently I've been recording some nylon string guitar for a track. I've been pointing the mic toward the 12th fret at about 8-12 inches away, and I have to say it sounds pretty good. Crisp yet warm, and pretty detailed. It sits in the mix very well without too much tweaking. Recently I read that a small diaphragm condenser is better for classical guitar because it captures more detail. So I guess my question is, it it really worth me shelling out for a small diaphragm mic, when I'm quite happy with the results I'm getting from the Perception 220? Would I be that much impressed by the improvement? Do you think the extra detail I'd get would be lost in a mix (drums, vocal, bass etc) and that it wouldn't be worth the expense unless I was recording solo pieces? 
 
Also, I kind of wish there was a little less room in my recordings. It's not that bad but I would still much prefer a dryer track on which to add my own reverb. My room is completely untreated and it looks like it's going to stay that way (ARC2 is spoiling me!). I've seen sound absorbers that fit onto the mic like this and reduce reflections:
 
http://www.amazon.com/Microphone-Diffuser-Isolation-Absorber-Griffin/dp/B0082DAL3S
 
But they're quite pricey. Is it worth it? 
 
 

I would be looking at ways to improve the room reflections in your recordings. I have a nice dead type space which actually works very well for acoustic guitar. You may find even with a small condenser you are still going to get a lot of room in your recordings.
 
If you can dampen down the room a little I think you will find you may get the most improvement in your guitar tracks including an improvement in detail as well. It is not that difficult or costly to do either and if you are renting there are ways of making it temporary too.
 
You can always add the space into a drier recording especially now with the plethora of great reverbs available.
 
Having speakers in a slightly live environment is also not that great either ARC or not.

It took me quite a while, experimenting with various configurations of mic placement before I really became half way satisfied with my recorded acoustic sound.  I still have quite a ways to go.
 
IMHO, getting a good recorded acoustic sound is probably the hardest thing I have tried to do.
 
Room matters. If it's too bright and reflective, that needs to be tamed. Simple curtains and furniture and carpet will go a long way towards making the room sound different. A totally empty room has a different "sound" as opposed to one with furniture in it.
 
Experiment with mic placement and distance. Try the ARC mic. It is, after all, a mic. It will sound different from the other ones you have, but it may actually get the desired results. Worst case, it doesn't make the acoustic sound as good as a different one. But, before buying a new mic or several new mics in search of the holy grail of acoustic guitar recording, try working on the sound of the room.
 
Be sure, as well, that you like the sound of the guitar in that room with your ears. New strings are one of the things that brings my acoustic guitars alive. So when I get ready to record something where the acoustic is going to shine, and not just be a background filler, new strings are the order of the day.

Here is a good YouTube video comparing many large and small diaphragm mics.  These are all profession grade but its interesting to hear them all recording an acoustic.
https://www.youtube.com/watch?v=04vdECGx-8k
 
Rimshot
 

Cakewalk have done an excellent tutorial on acoustic guitar recording here:
 
https://www.cakewalk.com/Support/Knowledge-Base/2007013311/10-Microphone-Placement-Techniques-for-Acoustic-Guitar
 
Check out the vertical spaced pair. That is way cool and I have tried it and it sounds fabulous. It works better if the mics are matched I think (but I am sure it would work otherwise too)

I like the small diaphragm used in a M/S config w/the small D pointed straight at the neck/guitar. The Side mic is turned figure 8 per the procedure outlined.  With good mics and good amps, you can capture a really nice warm and wide acoustic guitar performance. 

No, but this technique works really well for acoustic guitar.
 
https://www.youtube.com/watch?v=wiZFtN1xm-U
 
I use it when ever I record acoustic instruments, which includes guitar, dobro, mandolin. And flip it around to control left vs. right. Really good stuff...