I have been using 4 different cards on two computers over the last 2 years 2 x1900xt , 8800gtx, 9800gx2 ( sold it after 3 weeks, waste of money ) 2 x 9600gt and the single 8800gtx gave me the smoothest playing experience..
I would be getting the same mimimum frame rate of 15fps - 20 fps on my single 8800gtx, as I would on 9800gx2 @ 1920 x 1200, same would happen on 9600gt, only mimumum frame rates would be lower than 9600gt.
Now yee are talking about the amazing budget power of the 4850 and I've just my crossfire mobo for a sli one 6 months back....
Getting a bit pissed off at this stage with computing in general.