Amp Testing vs. speaker safety

I have a pair of B&W matrix 804's that have the biwire posts on the back. I want to a/b test a new amp in my setup with my old amp. the speaker posts have spade and banana plug connections. Presently the spade connections are to the prospective new amp. I would like to also run banana plugs to my old amp. I would then just switch the amp input (from my main outs on my pre-amp) RCA plugs from one amp to the other (of course turning off power to any amp before pulling out RCA input plugs) to test them. Would this proposed setup hurt my speakers, since only one amp would be live at any one time via the RCA input wires, although both amps would be connected by speaker wire? Also any potential harm to the amps with this setup. I will do nothing till I hear from my fellow audiogoners.