Go to the advanced tab in the gadget settings, and in the Select a Monitor drop down menu choose GPU usage. Then select Graph w/Title in the Display Style drop down menu
I purchased a Xonar DS a few months back, and I've been pleased with it so far. It uses the same C-Media chip (CMI-8788) as a lot of high-end sound cards. I researched it quite a bit before purchasing, and I also found that it has excellent performance for the price.
Since I mainly use...
There are a few cheaper amps like the Zalman ZM-RSA, Samson S-amp, Rolls HA43, Behringer HA400, ART HeadAmp4. However, I would suggest spending ~$100 and getting something decent. Here's a good site about headphone amps:
http://www.head-fi.org/forums/f5/
If your cards have reference coolers, setting the fan to about 40% should keep temps down. You can also use the Radeon Bios Editor (RBE) to set fan speeds at different temps, and flash the customized bios to your cards. Here is the guide...