If you are getting the UMC-1, then I think you should definitely get the XPA-5. No doubt about it, especially since aesthetics is important to you.
I think Rotel has more "prestige", but both will have the same sound quality.
But for aesthetics, the UMC will look much better with the XPA.
I think with the older receivers & pre-pros, separate 2Ch analogs sounded better. But with the newer receivers & pre-pros with the PURE DIRECT/SOURCE DIRECT modes, which bypasses all the tone controls, balance control, and EQs, I think you will get the same sound quality.
If you compare the specs of the Emotiva analog preamp RSP-1 vs the newer receivers in Pure Direct modes, you will see that some of the receivers (Denon, Onkyo, Yamaha) actually have BETTER specs - Freq Resp, THD, SNR, Crosstalk.
Yet, Audioholics gave the RSP-1 an awesome review-- FIVE stars for 2Ch audio performance!