I've just been using CCC. You can click the drop down box and pick the second card. Set the same clocks for that. I think riva sets both at once.

860/1251 VPU recovered in UT3 I was able to play quake wars for 45 minutes problem free before I got bored and quit though. After that I had checker boards in any game at any clocks until I rebooted. *sigh*