Hmm, if price is something your worried about, I'd say definately get an AMD processor (I still think Intel's are better...but for price for what you get, AMD can't be beat). Probably a lower speed processor, maybe a 2800?
You could probably get for a vid card a 9800 as well. I am a solid Nvidia person, but for price for quality, and what you might be after, go for Ati. Ati is more of a hassle and have terrible drivers (STILL, afterall this time, you'd think they'd finally start getting things right, but no...)...however, IMO for what you probably would be after, Ati is the better choice.
Go for at least 1024 DDR Ram, if not better.
Not much in specifics here, just general thoughts on the issues...I think it would be best however, if you go to your local big time computer shop where they sell parts, pretend you are shopping there, and ask about different parts...as well as cases and such. See for yourself which options you like best, and then as others suggest, buy online...but make sure you have a good return policy.