Antec has released a new line of power supplies that look nice. I would go with the 380 Watt version for your system.
The best way to figure out what size of power supply you need is to look at the motherboard requirements and the CPU requirements for current.
A switching power supply provides the cleanest power when running at about 90% load. Too big of a power supply can lead to a noisier signal, too little and the power supply will crowbar.
I like Antec. They have about the fastest transient response time I have ever seen in a power supply, which is very important in a high demand application. The new line of supplies has better over voltage capabilities, which is good for that all important power on phase.
They also seem to be rating thier new power supplies closer to what they can actually do. The 300W supply Skurj is using should have been rated 330W as the overhead for the supply was really much higher than a typical 300W supply.
For a brief time they had a thermally controlled fan, which was okay, but the new line couples thermal control with load levels, so they react faster to changing conditions. The addition of a second fan was not really needed, but a nice touch.
Anyway, you can read more about them at
http://www.antec-inc.com
