thank you, jd, batpig and Jchin
as I figured, the problem is . . . me
here is a "I wonder what would happen wrt optimization . . .
I use Sub 1 out to feed 1 channel of my Inuke6000 running the SubMaximis, I've got some DSP eq done there but it needs re-checking wrt the new X4000
Sub 2 is split, one leg feeds a signal to a BASH 300 running the 2 Clark shakers on my couch and the other leg feeds a BASH 300 pushing a 30" THTLP
I can run the Sub EQ and turn things on/off so the system can do the best work for each sub and then I suppose, run it again with them both on.
this is a which came first chicken or egg ? and each room and setup is different but anyone with any such back and forth experience is invited to speak up and put their .02 in
curious to hear what's been discovered . . .
addendum : some other info
Until I can wire the 2 THTLP's together (yes there is a second one) in a series parallel config to run off the other channel of the Inuke (at 8ohms I can still get about 1K to drive both and no they will not be co-located, it just more wire as my entire room is 14+ x 28 and total volume is 5Kft^3 . Too much just might be enough.