Ultra 500w Modular Connection PSU
Thermaltake 560w PurePower PSU
both are $100, I've built two machines with both and are wonderful. My machine which has 9 case fans, 1 on the CPU, 2 in the PSU runs OC'd with this PSU just fine. has a +12v rail of 22a which is generally always the weakest rail, but that 22a should provide you with enough juice for whatever you want. The ultra 500w power supply has a 30a rated +12v rail so that REALLY leaves a lot of extra room on the +12v rail and both have adequate wattage.
Regarding your mobo decision, yeah both are really good and really you can't go wrong with either. So hell pin up a piece of paper with ABit and MSI written on it and start chuckin darts