Good point. Guess we're talking about a 4PDT switch box that connects each amp to a load resistor when not connected to the speaker.

Don't know if anyone sells something like that so might be a DIY affair.

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8