If your mains are not being driven to their full potential currently with your amp then that's a whole separate issue I would takle first. I don't buy the statement that you should relieve the amp of low freq signals from the mains.
Step 1. Get an amp that can adequately drive your mains
Step 2. Worry about the other stuff
Step 1. Get an amp that can adequately drive your mains
Step 2. Worry about the other stuff