Not sure yet on connecting the 4870...I bought the Powercolor 1gb OC'd card (800/3700) and it does run much cooler that the reference models. The reason behind switching from the nVidia 8800 was that with the x38 board I can xfire 2 of the cards. So for xmas I will get a second card for my ultimate buildout. I won't be able to watercool 2 of the cards (not with the Feser 240 rad, I would have to get a 360 rad) But with the CPU, NB and SB all watercooled, I turned the case fans all on the RAM and videocard.
I have the vcore set to 1.2v...The Maximus Extreme seems to be off for CPU and NB voltages. On auto, the CPU volts were fluctuating from 0.98 to 1.1v. When I oc'd to 3.6, it started to stick on boot screens...So I bumped CPU v to 1.2, and NB to 1.4. This weekend I also installed Vista 64bit. I'll push the cpu to 4.0GHz and re-run 3DMark06. I need more ram though...I'm only running 2gb.