Don't know why it would not work, but for sound quality a second amp would work better. For that price, you could a used 5.1 channel amp and add several degrees of flexibility without worrying about impedance matching. In short, I'm worried the sound quality of your design would suffer.

Panny 3000 PJ, 118" Carada, Denon 3300, PS3, Axiom QS8, PSB 5T, B&W sub, levitating speaker wire