I agree with nate. Go with a single 12 + volt rail. I use pc power & cooling too.
Other things to consider:
In addition to the normal 24 pin eatx pwr, the RIVE also needs a 4 pin eatx 12v plug and a 8 pin eatx 12v plug. (another 12v plug if running quad sli)
if your running sli you will need x4 six pin pwr connectors for the x2 video cards.
plug in cable management on psu's aren't worth it.
Look for a psu with a good warranty, or purchase it from new egg incase you have problems with it. I've gone through many power supplies in my day.
Asus Rampage IV Extreme * i7 3820 @4.7 GHz (on air) * Thermalright Ultra-120 extreme (push/pull) * 16gb G-Skill Ripjaw z 2133 * Asus GTX 670 * Asus VG248QE * PC Power & Cooling 860 * Samsung 840 250GB SSD * x2 Mushkin Chronos 120GB SSD
