UPDATE:
I got feedback from Outlaw tech told me config sounded fine.
I ended up using the ICBM between my 3 channel (L, R, and C) B&K ref. amp and receiver pre outs. (Set all 3 to 80Hz, receiver on 'large').
I just 'hung' the woofer on the sub output, and set up sub on EXT but used the 36db filter on the ICBM. (sub is part of a THX system, M&K 750). Adj. sub to 0 ref., ICBM at 0 ref.
Ran audio test at 75db, sub put out 80 which is good because Avia has miscalibrated output about 5db to low.
Set my surrounds to 'small' in the DVD player so they will not pass below 100Hz. I don't have them externally powered.
Running 5.1EXT sounds excellent, but I did not loop back receiver sub output (LFE) to ICBM so I may be missing something. But it sounds great!
And stereo is incredibly good. My receiver was cutting off my mains at 100 Hz, way too high.
Now the sound is much better balanced, detailed yet smooth, and the sub sounds 'bigger' and more musical. Amazing changes!