needing new PSU

I'm needing/wanting to upgrade my PSU and was wondering what everyones preference was on a PSU. What is preferred a single rail model or multi-rail model?

Single-rail is more reliable, and I recommend Corsair. Nobody has made consistently better PSUs.

I personally think multi-rail PSUs for computers is a marketing gimmick. The idea for multi-rails is to provide isolation between the various systems supported by the PSU. That may be fine in big, commercial or government communications facilities, but not in a single computer. If you lose the rail to your graphics card, for example, it is not like the rest of the computer will take over and continue to support your computing tasks.

Multi-rail PSUs are MUCH more complicated, using many more components. For this reason, as Thrax noted, single rails are more reliable.

Also, on multi-rail PSUs, there typically is a reserved amount of power that always remains available on each rail - even if not used! While on a single rail system, all the power is available all the time. So a 650W single rail PSU can provide more power on the single rail than a multi-rail 650W PSU can provide on any one rail. This means in some cases, a more powerful (read: more expensive) multi-rail PSU may be needed when a less expensive (and potentially more reliable) single rail would do.

This does not suggest multi-rails are unreliable - at least not those from reputable makers. But the potential for component failure with multi-rails is higher.

I like Corsair too. An excellent blend of good quality and fair price. The only bad experience I've ever had with a psu was a Thermaltake working for 30 seconds before the acrid smell of burning plastic filled the room. I got to twiddle my thumbs for 2 weeks waiting on a replacement but that has been working fine since.

And TT is a good brand too. But sadly, Man has yet to learn how to create perfection 100% of the time. So even the best makers will have some failures. It is then how they handle their mistakes that makes the difference.

I like Gigabyte for example because when I had a board 6 months past its 3 year warranty suffer from leaky capacitors, they replaced the board for free - and they have had a loyal customer ever since.

A lot of the models offered by Corsair are private label by Seasonic and Channel Well

Seasonic makes VERY good PSUs and have for a long time.

Here's a very informative and concise article from Tom's Hardware: Who's Who In Power Supplies, 2011: Brands Vs. Manufacturers

Single Rail is the best way to go for sure.

I'd prefer single-rail, for some of the reasons given and because I don't think splitting the rails really provides that much "safety" in the case of a catastrophic event as it is claimed to do. If something in the PSU fails AND causes damage outside the PSU, then regardless of the rail configuration it's going to be catastrophic.

I would back Thrax on this, Corsair units are highly rated. The Corsair AX series are the best quality units around and got the best pick from http://www.jonnyguru.com/ last time I ran by there... he knows his PSU stuff and his reviews are as in depth as one can want.