If that process or is an i7 4770K then I'm good with that.
The ASUS part number you reference points me to an entire system unit. Is this your computer?
http://www.amazon.com/Asus-G10AC-US002S-ASUS-Desktop/dp/B00DVFMFR2
As I look at other links to that model number, it looks like that is the computer itself.
I understand your concern over the 500W PS, but the current generation processors and GPUs are consuming less power than they were a few years ago. That said, I think 500W leaves you little room for expansion. If you overclocked (assuming that's a K model Intel chip) and added hard drives, and maybe even a second 660 in an SLI config, then no, that 500W ain't gonna cut it. But if you just run it as is, it may be just fine.
If there was an amazing price point that you got in buying it, then it may be just fine. But if the price advantage was marginal, then I'd consider returning it and building from scratch. I or a couple of others here could help you config the parts. You may face a re-stocking fee (often 15%) for sending it back, though. Weigh that against just replacing the power supply down the road.