Summary: With aim of this PSU you can build silent PC, which will be able to run some seriously power-demanding applications - e.g. 3D-games :) This PSU can feed Quad-core CPU and 2 videocards, and still stay quiet. The only noise you will hear (assuming you have good heatsinks on CPU and GPU) is seek noise of your HDD(s)!
The modular sleeved cables ease the challenges of keeping the system tidy and aerodynamic for optimal airflow, which is especially important if you wish to maximize cooling with the slowest of fans for the lowest noise. To top it all off, Corsair offers a five year warranty, which is the longest for any PSU!
It's price seems high at first, but in fact it worth every penny!
Highly recommended if you would like to build power, but quiet system.

Summary: Purchased this power supply after reading JonnyGuru's glowing reviews of the HX 520W and 620W. Since he really puts his review units through the ringer and rates these units 9/10, you really can't go wrong with them.

Installed into a CoolerMaster Praetorian powering an overclocked 8800GTS and Core 2 Duo E6420 (3.5GHz). The modular connectors are a blessing - much less tangle in an already dense copper jungle. The fan runs quiet and the higher efficiency is great (it's noticeably cooler running than the less efficient Vantec ION 460W it replaced).

Some folks have reported a slight buzzing with some units but I have not noticed this on mine and Corsair does back this unit up with great support (they offer to exchange buzzing units at no charge, if I'm not mistaken).

Summary: I would add my firm agreement to the earlier reviews here, as well as the majority of feedback posted on major retailer sites. I researched this item throughly prior to purchase, being most impressed by an online review at a site focused on silent custom pc building with an extensive writeup about the two corsair power supplies, including thorough metering at various stress loads. This was very valuable as I do not have the technical background to perform such a series of tests.

Given the approval from such a thorough exam, numerous user experiences, and the listed specs, as well as the five year warranty, I feel this is a power supply that will juice all but the most demanding rigs with peace of mind. At 520 watts, and SLI certified, it seems future proof unless an uber-rig is designed that would need more power, but that will be the case with any power supply.

I highly recommend this product, it has set the bar high and met my expectations. I have experienced no problems with this quiet unit in the short time I have had it. It has ample power for my current needs and reserves to outlast my planned upgrades. The actual manufacturer of the power supply is highly regarded. The modular cables are great as they allow one to withhold extaneous cables that would interfere with airflow and cooling.

It is also attractively packaged and well organized with a carrier bag for unused cables.