Like most other Bose systems, it seems to route the signal through the bass module before it gets sent to the other speakers. This is not a standard hookup that any other receiver I know of can take advantage of. Not to mention, Bose often uses proprietary speaker wire. I think your choices will be to see if Bose will sell you another receiver for that particular system, or just chuck the whole thing and go with a setup that uses standardized connections and wires so you can upgrade components our at will.

This is one of the reasons I don't recommend Bose systems to people. There's no good reason to have these proprietary connections and wires... aside from keeping you locked into the Bose universe that is.