crossfire on AX78 is my psu powerfull enough

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my power supply was playing up in my main pc so i got a antec 650 earthwatt which arrived yesterday .
i going to be selling my 8800gt to mate in next couple of weeks and was going to buy either a radeon 4870 or 1 of the new 5770 .
would this power supply be powerfull enough to run a pair of these in crossfire mode as i just spent £65 on new psu and cant realy afford to be going out + buying another
system spec

AX78
Phenom 9950 B/E
4gb Corsair XMS2 (4x1gb)
Geforce 8800gt
1x 500gb HDD
1X250gb HDD
Audigy 2
2x DVDRW

[BUFF]

you do know that the 2nd slot will only run x4?

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you do know that the 2nd slot will only run x4?

yes i know its only x4 , would that make much difference to performance
as i was gonna get 1 card 1st , then add another around 2 months time