I'm running a 500W Antec Dual 12V PSU on 2 Opticals, 1 HDD, and a 7800GTCO by EVGA all on the A8N-SLI Premium. That is a great and inexpensive PSU if you do decide to switch. (Not to mention all my fans have LEDs on 'em)
I'd see it as less risky to go to a native 24-pin power supply design, despite the A8N's EZ-Plug (which I believe is meant to circumvent the 20-24pin issue, if I read the manual correctly). It will also be SLI Ready, and the Dual 12V Rails would definately offer more stability in such a case if you do wish to upgrade to Dual Video in the future.
I believe in the dual 12V Rail system 1 rail goes to the 4-pin +12V connecter which handles your CPU and then the other rail handles all peripheral connections.