If you turn the crossover off on the AVM30, you'd need to also turn the sub off and route the left and right channels through the SMS-1 - that way, the LFE track would get merged in with the mains' signals, the SMS-1 would split the signals low and high (80Hz fixed analog high-pass crossover on the high pass output for the mains and the adjustable low-pass crossover for the sub), and you wouldn't have to worry about data getting lost in the crossovers. I agree with Curt from AVS - either disable the SMS-1's crossover entirely for a home theater application like this, or at least push the crossover all the way up to 200Hz.