Tested & Sent Back:
MOTU MicroBook II
CEntrance DACmini CX
Benchmark DAC1 USB
Rapco Horizon Oculus Designs Digital and Analog Cables
APC & Furman Power Conditioners
I like to keep my analog audio cables and digital cables as short as possible and physically separated from power cables to keep the possibility of noise at a minimum.
If you also use your USB DAC with software VST/VSTi synthesizers and effects on the Windows platform, it may be best to try to find one with a dedicated ASIO driver with adjustable latency. CEntrance, RME, Benchmark, and Roland write stable ASIO drivers with low DPC latency. MOTU and T.C. Electronics sound great for the money, but their Windows drivers are unstable.
All genres (anything that sounds 'good') but mostly listen to Ambient, New Age, IDM, Classic Rock, Classic Metal, 80s Pop, Blues, R&B, Jazz, Fusion, Classical.
Acoustic and Electric Guitars, Hardware and Software Synthesizers, Cakewalk Sonar, Native instruments, Camel Audio, & many other software VST/VSTi plug-ins, etc.