Ehhhh, I wouldn't recommend Dell if it can be avoided. Horrible build quality, and given the trouble with motherboard-gate, I don't trust them, either.
In fact, I'd recommend avoiding just about all pre-built PCs - they may look good on specs, but they undercut on quality - low end motherboards, low end power supplies, limited upgrade potential, etc etc.
If possible, take a look at
NCIX - if you don't feel comfortable building a PC yourself, they'll build whatever you want, or you can choose from one of their pre-built machines. The advantage here is that you know what you're getting, and you can upgrade it as the financial situation and specs evolve.
Assuming you already have the monitor, you can build a half-decent gaming machine for 600-1000 depending on what you want. For the budget and future-proofing conscious, look at something with a Phenom II processor (Intel Core processors are better, but Phenom IIs are still good, and much more budget friendly - they're also better when it comes to futureproofing, too, since AMD tends to stick with socket types longer).
Don't cheap out on the motherboard. Get the best that you can afford. Video cards, memory, hard drives... all easy to upgrade, but when it comes to replacing a motherboard, you may as well just get a new computer.
ATI video cards also seem to be the way to go for the budget conscious. More or less on par with Nvidia these days, but generally cheaper.
