Verdict:

Cool, quiet, compact and modular.

We were so impressed by the Dark Power Pro 650W three months ago that we thought it crucial to find out if Be Quiet!'s more powerful PSUs were also good performers.

This 850W model is equipped with a bountiful six 12V rails, each rated up to 20A and with a maximum combined output of 68A. The rails are configured so that 12V1 powers the motherboard, 12V2 the CPU, 12V3 two of the modular disk drive sockets, 12V4 the other two modular disk drive sockets, 12V5 PCI-E1 and PCI-E3, and 12V6 PCI-E2 and PCI-E4.

A very quiet temperature-controlled 120mm fan cools the 180mm long chassis. Helpfully, all the modular sockets and cables are colour-coded, and there are four headers for adding extra 3-pin fans to your PC. Another useful feature is ECASO (Enhanced Cooling After System Off), which keeps the PSU's internal fan, and any fans plugged into the extra headers, spinning for three minutes after the PC shuts down.

All of the Dark Power Pro's rails output a stable voltage in our tests. Unfortunately, we were unable to measure the effectiveness of its PFC circuit or power efficiency, as it uses a proprietary mains connector, which isn't compatible with our test equipment. However, other Dark Power Pro PSUs are at least 80 per cent efficient at full load.

The Dark Power Pro's innovative features such as ECASO cooling and colour-coded modular cables mean that it's good value for money.

• Gaming Headsets - 26th September 2008
• Dream PCs - 24th September 2008
• Headphones - 12th September 2008
• Media PC components - 22nd August 2008
• PSUs - 14th July 2008
• Multi-GPU graphics - 20th June 2008
• CPU water cooling - 17th June 2008

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