A question for Exa might be, will their DAC operate as a UAC2 device w/o the ASIO driver.... or will it revert to UAC1 and it's limitations.
Their own ASIO driver is supposedly one of their claims to fame, but if you can't get it to work the DAC will not function to it's full potential.
As for hum, more channels means more cables which means greater potential for ground loops and hum. Balanced interconnects can help in these situations even in non-studio environments like home audio. If you have any video gear in your setup like a cable tv or satellite box the potential for hum is even greater. If you have any video gear, try disconnecting it just for grins and see if the hum is minimized.
Enjoy!
