I have to choose so please help.
i saw your other post regarding your pc and the question raised for whether you should go quad sli or not
As of right now the drivers are not optimized for Quad Sli, therefore you would be wasting alot of money on 2 very powerful graphics cards, in truth i wouldn't go crossfire or sli right now since Dx10 cards are coming out soon, i would recommend getting a x1900xt 256mb and then wait to get a pair of 8800GTXs or if you would want to wait for ATis new R600 graphics card,
but if you are set on getting your components now the X1950XTXs in Crossfire would be the best setup at any resolution, quad sli just hasn't developed yet althought that could change, there is no doubt either setup will dominate any game out today, maybe even oblivion