Attached is my xorg.conf file. It's... complicated. I have 4 monitors on two identical 460's. Consists of 4 24" 1920x1200 monitors. Screen '0' is the center screen. Screen 3 is directly above it. Screens 1 and 2 are rotated 90" on either side of screen 0. There's custom EDID's for two of the monitors, which you'd want to nuke. Also, I'm not positive the PowerMizer settings do anything other than default (I was messing with it..)
I also use a xinerama library that 'fakes' the two portrait monitors to appear to the system as two 1200x960 'monitors' apiece. It's a really, really nice setup
Do note that if both the monitors on a single card do not have _identical_ modelines (I got lucky, myself), that card will never 'throttle down' from the max performance level.
If your two cards (and your motherboard) works with SLI, you may to be able to use the BaseMosaic option or SLI Mosaic to get full acceleration, as well. The docs say it only works with Quadro's, but I've heard rumours it works with some Fermi cards if they're identical. My motherboard doesn't support it, and I'm rotating two monitors, so it wouldn't work anyway.
Anyway, I haven't read this whole thread but my conf might help you.