With FSX its all CPU
The 8800GTs 640 and the GTX 768 are 384bit memory buss cards... these cards are actually BETTER for FSX than the newer 9xxx series however with the 280 that may change because they will be incorporating a higher number of TMU's and a few other changes
The 9xxxx cards are a marking joke.. unless you are coming from a slower card their use in FSX is no better than the original GTS/GTX because they reduced memory, memory buss but increased TMU's so its 6 of 1 , and 1/2 dozen of the other
CPU and memory speed is what FSX needs and it does need the right card matched to that speed. You cant put a Q6600 quad with a 8800GT and get the same result as pairing that with GTX.. the GTX will squash the GT in a hearbeat 8x or 9x in FSX
Yeah. The 280 has 1GB GDDR3 w/a 512b bus. Very nice. I'm looking forward to the nehalems coming out at the end of this year, and the octo-cores next year. That should help FSX out a bit.