Simple question re; using two sets of speaker taos

Hi all,

I have an Accuphase P-300 as my main amp, running Thiel cs2 2's, and am considering hooking up a second pair of speakers to it. The P-300 can run up to three pairs. But I don't want to do so, if there is any chance that having the second pair hooked up could degrade in any way the signal going to my Thiels. I would not run the two pairs simultaneously, though this is of course possible. And I don't see how just having speakers hooked up to the B taps in back (about 20' of speaker wire per speaker) could make a difference to the A signal, but I've been wrong about this sort of thing before.

So, anybody?
Since the A/B switch will disconnect one set when the other is selected, there will be no degradation when either is played.