Do you really want 5V though? IF it's 4.91 idle and 4.91 with everything spinning, then you are okay, and you get like 2% less heat than if you were running 5V. Everything should be specced to trigger cleanly at like 4.75V.
OF course if you are running cool and light and get power flakies, you might want a higher voltage, if however you're running hot but stable as long as you don't turn the central heating on, then you might wish for that 4.8ish instead of 5.2ish.
It's something I aim to experiment with when I get a board with decent temp monitoring. Tuning the PSU.