Put TS cords in the XK1c and attach to a mixer and observe the output. Set the output so that you achieve -10db. then swap out the TS cord with a TRS cord, if the output is still -10db then it TRS cables won't improve the signal (because the XK's audio plug is not setup to accomodate the ring on the TRS plug). If you see the output on the mixer jump to near 0db then it accepts TRS cables.
Having formerly owned an XM2 module its outputs were TS, not TRS so my guess is that the XK1c is the same. One other clue, the "hookup" picture on page 17 shows TS plugs. they went out of their way to show the input plug going into the expression pedal as TRS. So that would be another indicator that the outputs only accept TS.