If you have the I2S Pro output on the transport, then most likely you have the UMT Plus not the UMT - two different models.
My dealer also swears by Ethernet streaming via UMT+ as opposed to using the USB 384kHz input on the DAC. Getting a separate PSU for the UMT+ video part is also said to bring considerable improvement.
The clock, as edorr already noted, is useless on the UMT+ if you already have the MSB DAC with Galaxy Femtoclock.
Adam,
I'm getting an UMT Plus soon
Please elaborate on this extra PSU for the UMT+ video part. Which one should be used?
alexandre