@gdnrbob -
A sordid, unhappy, long story, some of which can be found here:
https://forum.audiogon.com/discussions/vandersteen-2wq-subwoofers-with-m5-hp-crossovers-help-needed
I think you posted on that thread, btw. I am still working on resolving this. I suspect the amp is the problem, but I am far from certain. The new amp internals are surely burned in by now, and I am less than thrilled with it when run full range into my Ohm Walsh 2000s, which I know can produce pretty good, deep bass in my room without a subwoofer. I may have a 64 lb. paperweight on my hands. Worse, I don’t really have the money for a new amp (at least not one I would want to own long term). I have tried another amp, but it was vintage, and I could not find the input impedance. I am working with Johnny Rutan at Audio Connection to figure all this out. He has offered to stop by my house with an amplifier and see what happens, so I am waiting for him to have an evening when he has some free time. But it has been a very frustrating 6 months. I miss my rig. :-(