Strictly for accoustics, would I be better covering my walls with a low-nap (dark) carpet, or going with painted drywall + accoustic treatments?

My room is approx 19'x9' with approx 7' ceiling + tray. I thought 100% drywall would be too bouncy. I have a perf screen behind which will be foam surrounding the front speakers. Floor will be carpet. Ceiling will be drywall.

Anyone here tackled carpet on walls? How did it turn out?
Thanks!!

I'd definitely recommend the acoustic treatments over the carpet. You'll get almost no benefit from the carpet. If you are on a tight budget you can do acoustic treatments in stages. If you locate your primary listening position you are going to use in your room then have someone go along the wall with a hand held mirror and look for the speakers. That's where you'll want to place an acoustic panel. That method doesn't cure all, but it will give you a far superior room sound wise and will be the easiest and fastest way to get a significant upgrade in your theater.

Thank you! That is exactly the answer I was looking for.
So to prevent excessive echoes and phase-clashing, I just need a few well placed treatments?
I'll need them opposite the side-surrounds, obviously. Along the back wall too? From what I can tell, most build them from 2'x4' rigid fiberglass. Is there a rule of thumb for how big they need to be?

The bigger the better, but there's no rule of thumb that I know of. Here's the link that I share with everyone who asks about acoustic treatments.
http://www.ethanwiner.com/acoustics.html#top

I found it to be an excellent resource. Read this... more than once is a good idea. And you'll have a great grasp of what to do to optimize acoustic treatments in your theater.

good luck,
Craigo