Don't do it man. Amps connected to each other tend to look like short circuits. High potential of smoke escape.
My favorite solution for sharing one pair of speakers between 2 amps is to use a 4pdt relay with a coil that runs off your outlet voltage. Set it up with the speakers connected to the unswitched side, the default amp to the nc contacts, and the other amp to the no contacts. Energize the relay from the switched outlet on the second amp. As long as the second amp is off, the speakers will be connected to the primary amp. When the second amp is switched on it will activate the relay, and the speakers get switched to the second amp. I use this on a system where I use the same speakers with either a TV, or a receiver. It works fantastic, is automatic, and is a lot cheaper than an amp switcher.
I can send you a wiring diagram if you like. I use the Potter and Brumfeld relays with the socket base. All you have to do is connect wires to screw terminals. For the energizing cable just use a cheap extension cord with the end cut off.
gerG