D1100 claims to be quad balanced. It is single chassis.
Indeed. Same goes for the D100 and D150. However, those are all
Digital Preamps versus traditional full-featured preamps - of which I often overlook!
@kevzep makes some really good points about the balanced vs. non-balanced connection schemes and how they relate to common mode noise reduction. This can also be done with RCA cables between units when the preamp (or amplifier) utilizes a differential input section. Either way, noise that is common to both conductors is eliminated - like a 60Hz hum induced into a cable too close to the AC power cord of a high current appliance. So, I'm going to have to agree with kev in that the XLR inputs would be the way to go for the highest noise immunity. After all, his day job is in the pro audio world and XLRs and TRS connectors are the standard. He must have hundreds of such connections to deal with at a big show . . . and it just takes one to add noise to the entire PA.
The SQ stuff is an entirely different discussion. When using a preamp like the C47, which isn't a fully balanced design, only you can decide which you prefer the sound of - the RCA or XLR inputs. I've heard some prefer one while others prefer the other. As long as noise is no concern (and it shouldn't be with short cables), the end result will be to your liking. When using fully balanced components - sources, preamps, and amplifiers - the question begs, Is there better sound quality to be had as each unit in the signal path has mirror imaged sections to handle the positive
and negative halves of the signal separately. Obviously, such designs are more expensive as component count doubles in preamp and amplification stages. Some say that adds unnecessary complexity to the signal path while others say that adds performance. Again, only your ears can decide.