ur better off going with the 260 GTX I think, save a little more and get a 2nd one, the extra ram helps alot. Honestly I never believed it till I saw it.
2 9800 GTX+ will outperform 1 260, but the 9800 GTX+ just a 9800 GTX revision with a higher sticker price.
I personally think the 9800 GTX+ aren't what they are cracked up to be, 1 9800 GTX+ still struggles against the 4850, and the 260 GTX is 30% faster than the 4850, and its a single GPU
Thats what I think. Unless you got one of hell of a deal on them