which is better...right now i have dual 9800gt and i was wondering if getting a single gtx 285 would be such i difference i play the latest games out there like gta 4, call of duty, and crysis..etc... also my monitor is 1900x1200
No it wouldn't be much of a difference, unless you play lost planet which doesn't like multi card setups. The 285 is only slightly faster than the 280. Don't get a 285 unless you plan to get two and SLI them. Just save your money and wait for a DX11 card.