Hi:
I assume you are referring to the FetValve 350Ex power amplifier. Unfortunately there is no physical room for an additional channel in the chassis. The reason is that all of the available heatsink space is used (12 output devices) due to the high current capacity of the amplifier.
We do offer a three channel OmegaStar, the 240/3, that is designed to be used as a front amplifier in a theatre environment.
Thanks for you question!
Larry Jenkins