CORE 2 DUO E8400 3.0 Ghz
Asus P5N-D MAINBOARD
PALIT 896MB GTX275
4GB CORSAIR XMS2 DDR2 800
640GB HARD DISK
SOUNDBLASTER AUDIGY SE
ANTEC 900 GAMING CASING
SUPER QUIET 22dBA TRIPLE COPPER HEATPIPE CPU COOLER
rest of the standard stuff for around £800. You could probably use onboard sound, get a smaller PSU and knock off about £50 easily. GTX260 core 216 will also save you some cash while still giving exceptional power. Not exactly sure how much that translates to in dollars, but I think something similar to what I'm planning to get should fit your budget.
i am buying a Dell monitor separately. it does a huge 2048x1152 resolution, so my rig is specced to perform well in games on that resolution. If you are using a smaller monitor you could really save a lot on teh card by going for a GTS 250 or a 9800 GT or even a Radeon 4870 or something.
Oh. Just noticed you are going to buy from dell. I think its a lot better to buy from some other not-so-popular retailers. You'll get FAR more bang for the buck. Dell is very very overpriced for stuff like this. when you want to squeeze the last ounce of performance for the quid... or in your case, buck.
$1100 will probably get you a great gaming PC. but at Dell it will probably get you a very mediocre one.