I would suggest a plasma for gaming because of the faster response times but you'll have a hard time getting one for that price. I own an older model 37 inch Vizio (model VL370M) that I bought for around $500 new. You could probably get it for really cheap now. It's full 1080p and looks really nice IF you calibrate it (if not it looks like garbage). You could probably get a newer Vizio at that size and in that price range that is pretty good too. The problem you'll have with that size and price range is that you won't get a TV with a great response time (increasing the chance for lag and motion blur) and there will always be some issue with the picture. The response time in the model I gave you is like 5-8 ms which isn't great but I have yet to see motion blur. The issue I've seen is that even with calibrating the hell out of my TV some of the colors aren't great for yellows and the blacks have a bit too much blue and grey in them. The issue is that you'll have to compromise somewhere it's just hard to say where and how much.
Yeah, I think I'll just wait it out and buy a more expensive TV, or Cyber Monday or something.