Hi Masilu
The factory rep information is correct. The Capitole's single-ended outputs are converted to a balanced signal by going through a Burr Brown special line driver that splits the signal into positive phase and negative phase (pins 2 an 3 of the XLR connector).
I suggest that you use the RCA outputs of the Capitole, unless your cables are very long.
In your system, because your amp has RCA inputs, the RCA to RCA connection is the shorter signal path.
A XLR to RCA adapter will certainly degrade the sound quality.
Those with amps that have a direct XLR input will get better sound from the Capitole's XLR output, again because it is a shorter signal path.