Thanks Daryl and Gonk. I already thought about the preamp out to the sub and back to the amp but like you have said I then lose my balanced connections between the processor and the amp.

As for lowering the sub's low pass crossover setting. Neither the low pass nor the high pass crossover setting has any effect when I have the cable going into the LFE port on the sub. I have verified this by changing these settings while music is playing and only the sub is active. I have to use the SUB/SAT inputs to use the high or low pass filters on the sub.

Where do I change the 990's 2 channel sub offset? Would that be available using bypass in analog mode? I would think that all 990 crossover settings would be disabled in this mode as all outputs - speaker and sub are full range.