I'm confused. Are you going to connect two amps and two sets of speakers using each of them independent of each other (one amp off!) or are you talking about bi-amp'ing one set of speakers with two amps?
FWIW, some pre-amps with two sets of outputs can drive two of anything at the same time, some can't and those that can't and are put into service thus wired can cause the amp to put out a signal which can/will damage your speakers and/or the amp, or both. (I own one of the latter pre-amps (-:)
Before going forward check with the pre-amps manufacturer or distributor, or even a good techie who is experienced with your pre-amp.
FWIW, some pre-amps with two sets of outputs can drive two of anything at the same time, some can't and those that can't and are put into service thus wired can cause the amp to put out a signal which can/will damage your speakers and/or the amp, or both. (I own one of the latter pre-amps (-:)
Before going forward check with the pre-amps manufacturer or distributor, or even a good techie who is experienced with your pre-amp.