I've the hz30 (2560x1600) and currently use 1x 5870 1gb with it. Upgrading to Crossfire soon though.
With a 5870 1gb, I can run most games at max details at this res. Only thing I can't max out is AA/AF however. I keep AA at 2x - 4x and AF at 8x. Getting 50+ fps though.
Games I play include:
BF:BC2
Borderlands
Starcraft 2
DoW2: Retribution
WoW
and some other stuff.
Only things my pc struggles with is Metro 2033. Getting mid 20-30s fps.
This is using a i7 920 @ 4.0ghz.
With your SLI 470, it should be fine.
Rara