PSU for new mATX system

[ToastyBread]

I'll soon be building a new mATX system. It'll be a single-GPU solution to begin with, but eventually I may add another card. I wanted to see what anyone thought about some of the GPUs I've been looking at. The system components will be:

i7 920 (possibly OCed to 3.0Ghz0
ASUS Rampage II Gene
6GB (2GB x 3) Corsair XMS DDR3 1600
Samsung SATA DVD-Burner
2x Hard Drives (one 640GB, the other is 250GB)
5x 120mm case fans
Radeon 5850 (if I did add another GPU, it would be a second 5850)
Linksys WMP600N

So far, the Power Supplies I've been considering have been:

Corsair HX650W http://www.newegg.com/Product/Product.aspx?Item=N82E16817139012

Corsair HX750W http://www.newegg.com/Product/Product.aspx?Item=N82E16817139010

Silverstone Strider ST70F http://www.newegg.com/Product/Product.aspx?Item=N82E16817256045

SeaSonic M12 SS-700HM http://www.newegg.com/Product/Product.aspx?Item=N82E16817151031

I've generally always been a fan of Corsair PSUs, and I've heard good things about the SeaSonic M12 SS-700HM from friends who have used it. The Silverstone is primarily there because I like that they sell a mATX/HTPC modular kit for their Strider PSUs, and since this is a mATX system, the kit could help with cable management. However, it's far from being enough to be a decision maker.

Any input on those, or any other suggestions would be appreciated. I'd prefer to try and keep the price to around $150-160, but exceptions can be made possibly. The mATX case I'm using is the Rogue, and it comes with an extension bracket for longer PSUs.

 

[Zero82z]

The HX750 is definitely the best PSU out of that list. Other good choices are the Antec Truepower New 650W or 750W (if you plan on adding a second GPU; if you only end up using one, the 550W model will be plenty), and Seasonic M12D 750W.

 

[ToastyBread]

The HX750 is definitely the best PSU out of that list. Other good choices are the Antec Truepower New 650W or 750W (if you plan on adding a second GPU; if you only end up using one, the 550W model will be plenty), And Seasonic M12D 750W.

Nice, I'll probably end up going with the HX750 and using the extension bracket to help it fit more easily.

I know it's often mentioned about not running a PSU at more than 40% to 60% of its rated wattage, if I recall right. Does that apply for running it at a constant load, or frequently? I know that at first, with a single GPU, it'll be within that range easily, but if I were to add a second GPU, it seems like there would occasionally be the chance it'd go above 60%. Is this ok?

 

[Zero82z]

The 40-60% load thing is for extended periods of time. If you exceed that for a few minutes a day, it's fine. And anyway, you won't cause any harm to the PSU by exceeding that. You can run it up to 80% or so without running into any real deficiencies. Obviously a good PSU can run up to its rated power output without any problems, but it'll run hotter, less efficient, and probably won't last as long. But 80% is fine with most good units.