With your 430w PSU, you won't be able to run a 660 / 7850, have a look at the gtx 650 ti.
Umm no. The 7850 is a really low power drawing card, even though AMD recommends 500W thats with like an overclocked system. For his I3 and pretty low power everything else, 430W will be fine. I've had a CX 430 in my Core 2 Duo rig, and it works with a stock clocked 7850 just fine. Not too sure about the GTX 660 though.