If you're not looking for high-end gaming, and trying to save a few bucks, I'd recommend AMD all the way. (actually, I'd recommend AMD anyway

) You'll get ALOT more "bang for yer buck" if you build it yourself(you could build a "dream machine" for $800-$900). I run a barton 2800+ myself and have had ZERO problems with it.
Dell is a pretty good brand-they have good (although overpriced) hardware and excellent tech support. I'm not a fan of Gateway or HP-have seen instances where their software did not "play nice" with windows and/or other software.
With Christmas coming, and prices overall dropping, you can get a very nice box for the $$ you're looking to spend. Newegg is a good place to see what things are going for. When you think you've decided, you might post back and see if anyone can find a better deal for ya. Best of luck....