Re: TwinView disables PowerMizer?
Yes, you got it right.
I've TwinView too, using 1 DVI and 1 VGA Display an imho it really sucks, that the nvidia-driver is wasting my Money by needing more Power than neccessary.
If you don't mind a static clock, you can set the actual clock by using the tool "nvclock",
using this, by setting "nvclock -n 300 -m 100", for the same rates PowerLevel 0 uses, works fine for me and lowered my GTX260 Temperatures by 7-8 Kelvin.
Also the power the Card has on this clockrate is enough for a 1680x1050 and a 1280x1024 display using KDE4s Desktop-Effects under Jaunty. No Problems so far.
PS: nvclock also can adjust your FanSpeed ;-)