You just have to make sure you have enough rails to power each card, that's all I'd be worried about, unfortunately I purchased a PSU with only two 6+2(8pin) pin power connectors and I can only fit two cards, now i gotta go out and buy another one.
I ran into that as well. So I ended up with another PSU that was just laying around, ergo I was forced to buy the necessary gear to fulfill its existence
![Cry](https://bitcointalk.org/Smileys/default/cry.gif)
lol