Cons of using main XLR/Balanced outs for subwoofer?

How about the case where the balanced out provides the signal for the main amplifiers and the single-ended out provides the signal to a pair of subwoofers?  Both of these signals come out of a buffered, unity gain preamp.

I run my two subs out of the single-ended (rca) outputs from my buffer, and feed my main amps from the balanced outputs. To the subs, I run longer rca cables into Jensen PI-RX transformers and then very short XLR cables from the transformers to the subs. Looking at the Jensen graphs and spec sheets, it appears the SUB-RX transformers would have been a slightly more optimum solution to use with the subs....but not by much, and not by enough to worry about. I actually purchased the PI-RX transformers for a different situation involving a single-ended tubed preamp into SS mono amplifiers that had only balanced (XLR) inputs. You do need to be careful with impedances in those full-range situations since having too high an output impedance into the transformers can roll off the high frequencies.