upgrading PSU

I'm going to be upgrading my PSU and was looking for some suggestions and preferrences on them. Also, what is preferred, single rail or multi-rial?

Try running this:

Thermaltake Power Supply Calculator

I'm not necessarily advocating Thermaltake, but it will give you an idea as to what size you need.

As for single-rail vs multiple-rail, opinions vary. If you have the right kind of system and are good at figuring out load balance calculations a multiple-rail is OK in my opinion. I prefer having single-rail because I think it takes some of the guesswork out of it.

XFX has a short video touting their "EasyRail" system here:

Power Supply Series - Pro-Series

Also, if you're concerned about energy efficiency and heat output, you should consider at least an 80 PLUS Certified PSU.

Hierarchy:

80 PLUS
80 PLUS Bronze
80 PLUS Silver
80 PLUS Gold
80 PLUS Platinum

Ecos Plug Load Solutions

Seasonic are the best IMO. A lot of the supplies from other vendors are made by Seasonic.

Here is a list of Power supplies and who actually manufactures them:

http://whirlpool.net.au/wiki/psu_manufacturers

For general use, single vs multi-rail doesn't make much difference. With multi-rail you have to make sure you distribute the power across the rails, which is usually done for you by where they place the aux PCI-e power cables, etc.

Here are a couple of good review sites:

http://www.jonnyguru.com/modules.php?name=NDReviews&op=Review_Cat&recatnum=13
http://www.hardwaresecrets.com/page/power
http://www.realhardtechx.com/