Absolutely my dear sir. The GPU you are using is relatively low end as far as power consumption goes. Just one question, why the A10? It doesn't make much sense if you are running a graphics card, you would be better off with a FX series something or another. I am no expert on APU's but this whole thing just doesn't really mesh up for me.
Ah rats, because on an APU, because they already have a graphics chip built onto it you can crossfire it with another AMD discrete card, which would make use of the GPU on the APU. Now instead you are just going to completely disable the APU and treat it like a CPU. Overall what I am saying is that you probably should have done more research, and as well with the graphics card, I think nowadays the GTX 650ti is a better bang for your buck GPU. Anyway that PSU will do you fine. 750 W is a hell of a lot of power, even with a second 550ti, you shouldn't be anywhere near the peak of that box.
Wow I didn't even bother to check if the mobo supported SLI. I'm a bit of a novice. Overall I think your build needs to be thought out a bit better. django, do you know where I could find benchmarks for the A10 5800k + HD7660D Crossfire configuration? I wanted to compare them to a 550ti/ 650ti