Your problems with the bass management section confuse me a bit. From what I could see in the manual, the RR2150 does not have a subwoofer trim setting, so you'd want to use the sub's volume (or trim) control to balance the sub with the mains, but the sub signal should track the mains. The purpose of the crossover settings is to offer a more robust alternative to the crossover on powered subs - or just offering a crossover of any sort for folks with passive subs. The only way I can see to creating the scenario you describe is having an input on the sub that bypasses both, which is not something I've run into before. What sub do you have?