I'm using a 900w Antec and I have put my Fluke and an Oscilloscope on it. Haven't notice anything out of the ordinary.
I also have tried each card individually. I will try the latest and just install the Drivers without the extra's.
I run two cards because I like setting the graphics to the highest it will go with smooth game play. Others factors why I'm still using CF. If the game runs smooth on full graphics and I'm only getting 50-60 FSP then I'm happy with that. I've been running CF since 4790's and with very littles issues with CF until AMD released Crimson Drivers.