It's usually not recommended to up the PCI-E Voltage.. thats a good way to fry your new cards bro. I've been looking into that board and I have some friends that just got it. It's a beast, and it can handle some pretty high temps according to the MFGers.
I know that many many people have been buying a little 40mm fan and strapping it to the NB on those boards. but as long as you stay around 60 or less you should be good. anything above 65 and I'd begin to worry.
Get something like this, there is others, but get a 40 x 40 x 10. as the x20 is to tall. There are others but this is a decent CFM at a low dBA Newegg.com - EVERCOOL EC4010 40mm Case Fan - Case Fans
Good luck, let us know how it goes.