You'll need a real PSU.
Also, a GTX 460 768MB has markedly better performance for the same price (see Tiger Direct's Sparkle GTX 460 768MB for $139.99 - $35 MIR for $105 final).
EDIT: There's no reason to overclock your CPU because you get one of these cards. None of them will tax an i5-760. You should overclock because it will make everything else faster.