Doesn't running 2 monitors Split your GPU resources? I remember playing some older games that support dual monitors and they just crawled. I also used to game on one monitor and have Aim on the other monitor and still crawled a bit. I wouldn't put anything on the 2nd monitor and just let it go blank. That way all resources are on your Primary monitor.
When you say you temp monitors running on the other display you mean you have your desktop visible? I would recommend an OSD of some sort. Riva Tuner is quite nice and what I use to show FPS and temps while gaming. It put items in the top corner so I can see them.