CX600 shows 46A on the 12v rail, and your looking at about 40-46A total, that's cutting it real close. Here's the (rounded) math, each HD 6870 has 151W TDP (~13A each) the CPU has a 125W TDP (~11A), the fans, HDD(s), optical drive etc would probably come close to taking up the rest - I know I wouldn't try it