Wiring one set of speakers to two amplifiers puts the low output impedance of each amp as a load on the other amp, nearly a dead short!
Result, you will blow up one or both of the amplifiers, and depending upon the failure mode, damage the speakers too!

Don't do it.
Using a DPDT switch at the speakers wired with the amp inputs at each end and the speakers in the middle set of switch lugs could work, assuming you can find a switch of adequate rating (one hundred watt amp and five watt switch likely is bung). Make sure it is a "break before make" switch design.
Frank Van Alstine