Help me choose a PSU

This should serve you well:
http://www.newegg.com/Product/Prod [...] 6817139005

Corsair is a reliable brand and provides a lot of power on the +12V rails

That being said, this is cheaper and still good:
http://www.newegg.com/Product/Prod [...] 6817341018
^I have the 600W version of this. It is modular and serves me well.

Both of course are probably a bit overkill but you didn't mention the rest of your system so better overkill than underkill. Plus overkill will allow for more efficiency and some room for upgrades to more powerful components. You could easily get away with the 400W corsair or the 500W OCZ modxstream though.

Thanks mate. Looks good. I'll go for it. The problem is, the price is sky high on electronic goods here, $150!!! That's why I wanted a 500 watt PSU, because its cheaper. Thanks anyway.

Not like I'm gonna buy this power supply, but what about a Tagan Stone 600W Power Supply. And I calculated the power supply requirements, and I need 470 Watts, according to the calculator.

188W is the max draw of the radeon 5870. 16Ax12V=192W
most high end CPUs are about 125W TDP. 12*10=120W

As for your 30 machines, you are taking that measurement from the wall. That means 120V. If 30 machines are drawing 25A total from 120V source that is about 3000W.

Point Taken... (Woah)

Here are the official power requirements for the ATI Radeon HD 5850 and HD 5870 video cards.


ATI Radeon™ HD5850 System Requirements:

PCI Express® based PC is required with one X16 lane graphics slot available on the motherboard

500 Watt or greater power supply with two 75 watt, 6-pin, PCI Express® power connectors.

600 Watt or greater power supply with four 75 watt, 6-pin, PCI Express® power connectors for ATI CrossFireX™ technology in dual mode.


ATI Radeon™ HD5870 System Requirements:

PCI Express® based PC is required with one X16 lane graphics slot available on the motherboard.

500 Watt or greater power supply with two, 75 watt, 6-pin, PCI Express® power connectors.

600 Watt or greater power supply with four, 75 watt, 6-pin, PCI Express® connectors for ATI CrossFireX™ technology in dual mode.

The power supply recommendations are for an entire pc system.

Corsair and Seasonic are two brands that have a reputation for high quality power supplies that consistently earn high marks in technical reviews. They are reliable, stable, and come with a 5 year warranty. Some of the newer models come with a 7 year warranty. Lately we've been seeing a few other brands offering some high quality units. One example would be the Antec Earthwatts and the Antec TruePower New series which are major improvements over Antec’s older psu’s like the Basiq models.