What is your current power supply? Brand and model? How many amps on the 12V rails?
Model is Tacens Radix V-550, it has two 12v trais, 12V1 and 12V2, both working at 20A. -12 at 0.5A.
THe 650Ti boost is doable on your current power supply but i would recommend at some point upgrade it to a better quality. Stick to brands such as: Antec, Corsair(AX,HX or TX series only), Seasonic or XFX