OK, as you know me, I would be modeling the distance in VISIO, just my anal self… A meter should be fine to test the theory. I would next make sure you can do this by doing a search on RCA & XLR & DSD & simultaneous… when all else fails, read the manual… 
So the answer is you can use both; however, they will have a difference in level by as much as 6dB; however, the Woo Audio HP amplifier is accommodating with level (low/med/high). Understand, if you do this experiment, there will be an initial difference in volume you will have to adjust for…
Adding post about sub for completeness, thought I remembered… getting old sucks…
Badbeef and Elk handled that inquiry…
RCA & XLR Output