I managed slightly better FPS when i added my second GTX280 in FSX but i have my effects spiced up. Biggest earnings were a change from the E8600 to the i7 920 and modification of the configuration file in order to make FSX aware of all 4 cores. FSX is very CPU dependent as we all know. My framerate in loaded scenarios can go as low as 20fps but in open sea raises to 70 sometimes as there's nothing there :P