The only issue I've had was to many splitters on the same output. I use a Cary SLP-05, C2500 and a C22 (vintage). The C2500 (with some sub plates) the signal is to weak to run multi signals on the RCA side of the C2500. The XLR side of the same output didn't suffer the same affect that the RCA did. I used all 6 XLR outputs and the unswitched pair went into a bass management system. It contoured 280hz and below with two column of 8" drivers (16 total) and 4 double servo units.
I recommend using a left and right signal from the preamp too. Not just 1/2 of the signal. The bass is laid down in stereo and sometime stereo + (they will image a center channel from 100-300hz). Below 60-80hz the signal is in stereo though it produces a omni perception of MONO. It's not, but for all intents and to simplify it, our brain says "everywhere". The schematics say otherwise..
The C2500 has adjustable gain on the line in. It's to contour the loudness (gain) between sources. I'm not sure on the output except in HT bypass it is set to a certain gain..