Unless you want to get the F12 and another ML, then let the ML be MBM. Then the F12 could have 40/50hz and under, the ML could have 40/50hz to the crossover of the rest...by using one of these... http://www.amazon.com/Behringer-SUPER-X-CX2310-Crossover-Standard/dp/B0002E58BK/ref=sr_1_1?s=electronics&ie=UTF8&qid=1357250915&sr=1-1&keywords=behringer+crossover Essentially your AVR sub output would go to that...then it gets set somewhere along 40-50 and sends the appropriate subs what they are good at.