I made a thread about it when I got my 260. Basically, two things will keep your card in 3D mode. One is running dual monitors, two, certain applications like "windows remote desktop" will also kick the card into 3D mode.
You can manually create custom profiles with rivatuner, create shortcuts to them on desktop and manually execute them. However, all you can adjust is GPU and memory frequencies, you cannot adjust voltage. So while your temps will go down, they will only go down by a couple of degrees at the most.