if you are running 2 GTX560's, that power supply is enough. However, if you are running the 3rd 9600GSO or SLI'ing 2 of them at 37a...that is still short by at least 20a. You need to make sure you add the amprage before you buy. That PSU is only rated at 54amps. So, the GTX560's both take 24 amps (48 max total), and 37 amps on the 9600GSO (all 3 running at 85amps, or 2x's 9600GSO 74amps). If you truly need all 3 cards running, i would recommend a Corsair 1200W 80 PLUS GOLD CERTIFIED psu. That will cover all your amp necessities, and run quite fine.
*Please correct me if i am wrong in anything i am saying, but as far as i know, you add the total of recommended amps per gpu. Hope this helps.