5870 CF? *puts on Clarkson voice* ... POWAAAAAAHHHHHHH.
Yipes that is just stupendously powerful.
I definitely think that you need to find games that are harder on the graphics. Or perhaps even the whole system. COD4 hitting 600 makes that bench utterly worthless now. Might as well bench Quake 2
Dirt (original) is heavy on systems, so I imagine Dirt2 will be too. Maybe swap Grid for Dirt2, or even NFS Shift.
Crysis and Far Cry 2 still get it done in FPS terms. Can't think of much in the immediate future that's close. Apart from Crysis2 obviously.
CoH is still heavy for RTS' although Dawn of War II can potentially push a system harder.
Mirrors Edge can be hefty with decent settings, even if it is old.
I've not tried Flashpoint 2 or the new update for Stalker, but I imagine they'll be pretty hefty too.
I certainly think the time to retire Grid, Quake and COD4 has come.