@p35 is very new platform. it has support for ddr3 ram. p965 is tried and tested. i guess its better to go for p35 mobo....
I guess u should go for E6750 since there is no cache diff and u can easily over clock it to the speeds of e6850.
The best card NOW for 6-7k is the 8600GT, but in 1-2 months, it will be the 9600GT. if u can extend ur bugdet by 2.5k, itll be good to go for 9600GT. infact this is much more advisable!!