I think I found a solution and from an unlikely source. First, these speakers don't go down to 40 when they are 3' from the walls which is how they are set up as this presents the most neutral sound albeit at the expense of a bit of bass.
I'd picked up a Gallo 8" passive sub to throw into the home theatre system but the lady said NO and that was that (already one powered woofer). So, I moved it into the stereo system and ran a RCA cable from the output of the preamp in parallel with the RCA to the SET 300B amplifier into a Creek passive preamp. This then feeds a Bryston 2BLP 60wpc SS power amp; the creek provides the volume control. The Gallo has an internal passive crossover that is crossed at 120hz; I did not think it would work well at all. BUT IT DOES! The Gallo is 8 ohms and low 90s for efficiency so the Bryston works quite well with it in stereo mode running into the sub inputs.
I reset the REL Strata II to cross over at the mid 30s. So, the REL works the sub bass and now sounds fine; the Gallo works the midbass from around 35, or so, up to 120. The lowthers do the rest. The REL is set to reverse phase.
It sounds great; bass is tight and well defined. The remote controlled Creek allows the mid bass to be changed easily for each recording.