what's ur problem man ??, if two 7600GT is better than 7900GT in oblivion, it doesn't mean that it is better for all games
i saw benchmarks between 7800GTX and two 6800GS few months ago, and 7800GTX outperformed the two 6800GS.
and since 7600GT is about the same as 6800GS in performance, and 7900GT is better than 7800GTX, i conclude that 7900GT is better than two 7600GT.
and by the way i don't thing there is a bid difference between 21.4 and 21