Generally, one USB port provides enough power for the DAC and amplifier in the Centurion Audio Station, just like some portable hard drives which require two USB connectors - the second connector gives you better stability and compatibility especially when you are connecting to a laptop. Sometimes 500mA from a single USB port isn't enough to drive the Centurion, up to ~580mA is needed if you turn the volume and lighting up to full. Ports for some devices may be very close or even just below spec.

Depends on how well the audio solution is implemented, having the DAC farther away from other electronics inside your PC or laptop is a good thing since there is less interference. Issues with USB audio are a thing of the past ever since asynchronous audio USB mode in 2007. Some of the best DACs are using USB nowadays.