Yeah, my old Seasonic Super Tornado 400W which has 22A on a single rail runs my 8800 GTS just fine. Although I don't know that model anymore, Enermax always made quality PSUs in the past so you'll be fine. With a "600W" no-name PSU I'd be careful, but Enermax is good stuff (or used to be, when I was more up-to-date 😉 )