Cons of using main XLR/Balanced outs for subwoofer?

2 followup questions to your helpful response. The straight Rowland to Revel connection would be balanced. Are you thinking the balanced to single-ended interface inside the Revel might not provide ground isolation like the transformer so hum could show up downstream in the daisy chain? Second, any significance to fact my Jensen PC-2XR is rated flat to 10Hz vs the flat to 1Hz of the SUB-1RR?
Thanks 

@milarep Yes to both questions.
The 1Hz response will insure that you have no phase shift at all at 20Hz or even 16Hz. Phase shift in the bass will cause a lack of impact. The transformer rolling off at 10Hz will exhibit phase shift up to about 100Hz.

I am now way beyond my knowledge base and hearing the voice of common sense confusion- which could be just confusion, nothing more. You indicate that transformer roll-off will cause phase-shift up to about 100Hz and this is important to avoid. The frequency response of the Rowland's outputs is 5Hz-70kHz -3dB @ 8 ohms, so seems appropriate to output into the Jensen transformer (the SUB-1RR) with flatter F-R response. But immediately downstream from that transformer could be either a Dayton SA1000 amp which doesn't appear to have flat rating below 18 Hz ( its specs are hard for me to understand) or the first sub in a DBA chain (unlikely to have flat rating to less than 20 Hz for my system). Furthermore, setting up a "swarm" DBA usually involves intentionally producing a mix of different arrival times from the subs by adjusting position, phase, polarity, closing ports, etc. Duke always says the ear is very forgiving of small timing errors in the low frequencies such that the speakers + room = a minimum phase system. So I am unclear how a phase shift in the low (< 20Hz) bass is consequential. OTOH he also notes that the ear has exaggerated sensitivity to frequency response errors (non-flat curve below 20Hz) in the bass region, so maybe that is what you are trying to tell me. FWIW, Rowland recommended the 2 channel Jensen transformer for running subs off the balanced outputs in my Concerto (but that was 14 years ago). I again want to say I will be running my Salk mains (+/-3dB at 33 Hz) full range, no high pass crossover. I appreciate your efforts to understand my options.

Duke always says the ear is very forgiving of small timing errors in the low frequencies such that the speakers + room = a minimum phase system. So I am unclear how a phase shift in the low (< 20Hz) bass is consequential. OTOH he also notes that the ear has exaggerated sensitivity to frequency response errors (non-flat curve below 20Hz) in the bass region, so maybe that is what you are trying to tell me.

Duke is right; phase shift is different from delay, and 'yes' in that order :)

Apologies for not asking clear questions or understanding your brief answers, which prompted me to learn what a phase shift in a transformer means. I found a Floyd Toole article (Audibility of Phase Distortion) which reports studies showing that "Within very generous tolerances, humans are insensitive to phase shifts. He also points out that in a normal room sound is reflected many times from objects at multiple distances resulting in enormous amounts of phase shifts that dwarf the far smaller phase shifts in amplifiers (a lot of this read like Duke's take on this). Rowland tells me transformer bandwidth in this very low bass is not important for their solid state amp's line outputs. I did read that a possible exception to this is in valve amps that use a high level of negative feedback, which may be relevant to your fine Atma-sphere products. I thank you for spurring me to learn more. Decided to use my older Jensen 2 ch transformer.