SLI GTX 480 power

So Right now I have:

8 gigs of gskill sniper 1866
Phenom II X4 975 @ 4.3Ghz
990fx Sabertooth
eVGA GTX 480 (OC to 875MHZ)
all in a haf 932 filled with fans

For power I have:
Corsair CX 600
And a FSP power booster x5

For my next upgrade I want to get another GTX 480 and aftermarket cooler for each to overclock (probably arctic twin turbos)

My question is if the power boster x5 can power these two cards or if I can plug the 8 pin from the X5 into the second card and the 6 pin from the corsair. (I dont know if this is possible, but i thought maybe it would stress each less, But I have a feeling that wouldn't work)

I really dont want to buy another power supply because im really stretching my budget with another 480



And please, dont tell me to buy an intl chip. You may have valid, logical reasons but its just irrelevant in this thread.

I also don't want to buy a new card unless its less than a gtx 480 (sub 200) and can outperform SLI GTX 580s

Thank you for any and all help.