Re: $1500 Upgrade
Took the offered advice, and installed a Sata DVD drive so that the 8800gt now fits on the bottom pciex8 slot. This has reduced temps, the 8800 has dropped about 8 degrees, and the 470 also dropped 6 or 7 degrees.
This is one of the factors I missed in choosing a mobo. Almost always forum posts suggest components for cost and stability, whereas layout is super important. I won't make this mistake next time, shouldn't have overlooked it at all.
Thanks to all your help, my machine is running great.