Upgrade or not?
I use Nvidia or ati, my last rig have 2 4870x2, now I have 2 EVGA GTX 480 in sli.
they work very well, I play games at max details, I have a U2913wm 2560x1080 and a secondary monitor 1280x1024.
Crysis maxed out whit msaa 2x play very nice (I don't say I have 60 FPS, but...