If I understand what you mean, and if I remember correctly (and somebody will have to corroborate this), it is NOT A GOOD IDEA to hook two amplifiers to one set of speakers at the same time. Don't do it until somebody with more knowledge than I says it's OK to do so. You'll probably need some sort of a switch box to connect two amps to one set of speakers.

Jack

"People generally quarrel because they cannot argue." - G. K. Chesterton