The Antec fan is thermostatically controlled, sleeve bearing fan. In most unit, it runs at very low rpm and does not speed up until after the air goes above 95 degrees F, which is not good for most computer. When the thermostat is disabled and the fan runs at full speed, it is pretty loud.
You can buy power supply with dual cooling fans for under $100. Or you can switch to the SuperMicro 760A case.
(1) Enermax EG351P-FM Dual Fan Noise Killer Power Supply ($45-60 retail)
Two Visible Ball Bearing Fans (9cm & 8cm) operate in push-pull mode to obtain high air flow at very low rpm. Fan Monitoring (FM) Function Thermal Control Fan (8cm Fan On/Off by M/B)
http://www.enermax.com.tw/power.htm
(2) SuperMicro SP301-RA Redundant Cooling Power Supply (Available with SuperMicro 760A case only.)
The redundant cooling system includes an additional back-up fan, which operates independently from the primary fan, and a thermal control circuit that includes a solid state temperature sensor. This sensor detects ambient temperature changes inside the power supply, and is connected to the fan power drives of both the primary and back-up fans. The thermal control circuit works with the temperature sensor to trigger a response whenever specific high and low temperature thresholds are exceeded. This circuitry enables the primary fan to
increase its RPM simultaneously with increases in the ambient temperature until reaching full speed at 40°C.
http://www.supermicro.com/PROFILE/PressRelease/press041599.htm
You can find the Enermax PS from Russ at Compucheap by mail order:
http://www.compucheap.com/cgibin/shopcart/shopper.cgi?preadd=action&key=msc05
I have seen this PS in many stores in southern CA.