I see the HD6870 uses less power than the GTX 460 1GB. I'm going to wait for the GTX 560 release and see how it compares to the HD6870. Found this thread: http://hardforum.com/showthread.php?t=1540093
so hopefully OK on power supply. If I have to upgrade the power supply I know I'll probably be tempted to SLI/Xfire
Thanks Pallimud, infernox, G00fy!