^^ If you are using one sub, as in 7.1, and XLR connections, you can use a single DB-25 switch box, like this:
I am using DB-25 to XLR cables from Seismic Audio
, and they handle 8 channels each. You'll need 2 of the female cables for input from each unit, and one male for output to the amps.
Re sound quality -- I am unable to detect any degradation. I am using 2 such boxes, one for XLR connections to main 7-ch amps, and another for RCA connections to 4 height speakers and subs. The RCA switch is noiseless. The XLR switch makes a sharp snat (one sharp click) when I change it. I guess there's more of a DC difference between the XLRs in the 7702 and SSP0-800 than the RCAs. If the music/movie is a decent loudness, it is not bad. Under quiet audio, it's annoying. But it is not harmful, and can be avoided by switching when the amps are off or muted (IIRC the Classe amps can be muted).
If for some reason you want better switch contacts, or want remote control. this option will drop right in to replace the data switch and can use the same wires. Can either cut off the DB-25 connectors and wire them into the Pheonix connectors, or get 3 of the breakout boards shown below. It will still make the audible snat, though.