I totally agree with Numby on the Alvarez. I bought a RD20S off Craig's List for $175, and I couldn't be happier with it. I've played $500-1000 guitars that impressed me less. Easy playing, extremely well made, and the sound is very nice. I've played guitars that put it to shame, but they were mostly $1500+ Martins. The concept of "sounds $1300 better" doesn't exist in my world.
The important thing about acoustics is to make sure the top is solid wood, it's usually mentioned in the specs if you look up a model on musiciansfriend.com, or a similar site. Older laminated top Yamahas have a good rep, though. The quality of Asian made instruments has improved dramatically over the last few years. Japanese and Korean made are better than Chinese, but most of the bigger American companies run tight operations overseas, then have the finishing work done in the States. Yamaha and Seagull also make some very nice (if unspectacular) acoustics for reasonable prices.
I'd start by going to the biggest music store near you and play a bunch of different makes to see what grabs you. Play a few that are out of your price range, just to see what a top quality guitar sounds/feels like. When you find a couple models you like, look them up on
Harmony Central? - The #1 Online Community For Musicians in the user reviews. The bigger online retailers (Guitar Center, etc.) usually have reviews as well. I would pay more attention to reliability than anything else, any structural problems with an acoustic guitar will be a pain in the ass. Definitely check out your local Craig's List, there's a lot of people selling off guitars to pay the bills. Take your time, and you might catch a great deal.
Once you get the guitar, be aware that strings and picks will have a huge effect on the sound. I've used Martin SP strings on different guitars, and it made them all sound better; plus they last long. The harder the pick, the more sound you'll get.
If you have any specific questions, post them or PM me. Good luck!
EDIT: after looking at the link posted by Numby, I should mention that "select spruce (or other wood) top" is code for laminated (AKA plywood). If it's a solid top, it will be clearly stated. Not that laminate tops are bad, but generally the tone is a bit flat, and they won't improve with age, as much as a solid top.