+1 I had a similar desicion between 2 Ati 4850s or a 4870....
Simply put yes you will have better performance today, but as always with buying older tech....its going to become obsolete alot faster, whereas if you go with the 260 you will for sure get more consistant frames, no worries about having to make sure all the games you play are Sli compatible, and eventually you can double up which would blow any 8xxx or 9xxx Sli combo out of the water. With the 9xxx combo, once you peak out performance ull have to scrap both of em and buy all new cards. As I see it going with older tech is really just buying time.....