Thanks for all the ideas!

I think I'll go with this one:

http://www.amazon.com/gp/product/B005F5U86G/ref=ox_sc_sfl_title_1?ie=UTF8&smid=A2LM6ZPY06LT1N

Sounds perfect for an always-on desktop amp with its tiny footprint, cool running, and low power consumption.

From what I can tell, the sound quality should be excellent, as with any well designed modern amp, and power should be more than sufficient for the small space and intended use.

I'm hesitant to go with one of much cheaper (too cheap?) digital amps using the same chip, and anything bigger would be overkill.

I'll report back once I have it in service.