Have a look at the GT275. The overclocked edition seems like a good contender to the 285-290 cards. and the price is not too bad.
These were my specs for my machine, you may be able to do better, with a better case more HD space, better mobo, and maybe even 2 gfx cards. But I suggest you use the extra cash to get yourself a bigger screen, The 2333sw is nice but I think I would have preffered a bigger screen.
CPU: Intel i7 920
Motherboard: ECS Black Edition
RAM: 12Gb's Corsair
Graphics: Zotac GTX 275 AMP! edition
Hard Drive: Seagate 1TB
Case: Coolermaster RC335
PSU: PC & power cooling 750W
Optical Drive: Lite-on DVD writer
Keyboard: Alchemy Illuminati
Mouse: MS sidewinder X3
Screen: Samsung 2333SW
Total cost: R 17 060
Purchased from IkonicIT......They were the cheapest.