cross fire and sli always has some problem whit serten games and also takes a bit longer for drivers to ceep up. youl probebly see fps building up whit time.
well fermi, no the 400 series is a power eating toaster still cant find eny ide why the 295coop stoped they still rule quite bad.
alto the sli in my experiens always been better then crossfire. but all in all i haw gone from sli and crossfire altogether. i noly go whit dual gpu cards much better. and easy to water coole lather on.
For your resolution 2 HD 5750's won't even show their full potential,get a new monitor and you'll see how they will perform.
But even if you want to upgrade it,first upgrade your monitor because for that resolution 2 5750's won't show their full potential nor can other more powerful cards like 5870....
And yes a 5870 is faster than 2 5750's but the difference isn't huge
A single 5870 should be faster than two 5750s, but at 1440x900 it wouldn't really matter since right now both are way overkill for that resolution. You CPU is the limiting factor here, but as long as you're getting over 60fps you won't really see a difference.