06-20-15: MattnshilpMatt,
...he suggested I add a sub to the room connected in series from the amps to speakers (high output terminals). He specifically said not to pull the signal low level from the pre-amp. He said to put the sub behind the listening position in the back of the room to balance the pressure in the room, adjusting the output so its not even audible but enough to offset the main speakers output pressurization.
As far as placing a sub in the rear of the room is concerned, it seems worth trying but the concern would be that arrival time differences at the listening position, between the mains and the sub, may compromise coherence unacceptably. And if you set the sub's volume low enough to prevent that, you may find that it is ineffective with respect to its intended purpose.
Also, regarding the reference to "series" connection (which strictly speaking is a misnomer, as from a technical standpoint the sub and mains would be connected in parallel): Assuming the amps are in the front of the room, as you most likely realize it would be best to connect the amps directly to the main speakers, and to run separate connections from either the main speakers or the amp to the sub. Also, as you probably realize, if the sub is a powered one the cables to it would not have to be heavy gauge (even 22 gauge or smaller would work fine) since powered subs have high input impedances (e.g. 10K or more), and hence draw very little current.
Regarding the BagEnd product, if you haven't already seen it you will want to check out Kal Rubinson's review. Also, you may want to look into the Spatial Black Hole. I have no experience with or particular knowledge of either product.
Good luck. Regards,
-- Al