As of right now, the q6600 is the best cpu on the market as far as price vs performance. Lots of programs are multi threaded now to make use of multiple cores.
Striker is overkill and close to 300 bucks. The evga 680i board is more than enough for SLI. Also, as im currently running SLI, a single GT card is more than enough, so i would advise sticking to a single GT and a p35 board. The abit you linked earlier is a good board to go with.