Well, not so much a "full" report since I just got the B1200D yesterday and set it up last night, but my first impression? O...M...F...G!!
I knew from reading this thread that the little 1200D could indeed make a difference even in systems with multiple, large subs...but I just wasn't expecting what I experienced last night.
I have 2 PSA T-18s (front corners) and 2 PSA S3000s (rear corners) and I have never felt mid-bass like this. I have tried both a S3000 and a T-18 directly behind my chair, but neither came close to the little 1200D. It must be due to the ported design, that's all I can think of.
I haven't done any real setup yet, basically I just split the signal from one of my rear subs, plopped it down behind my chair and turned it on. Gain is set to 9:00 (level matched with the other rear subs, 75dB @ MLP), boost at 65hz (straight up), phase at 0. Still need to get out the REW rig and measure the response, but not really sure if I want to...it sounds so good now, and if I see an ugly graph I may change things so that it doesn't anymore.
Played a bunch of music, and then bass clips from the AVS demo discs. Music sounded great! The mid-bass was much more "punchy" than before, but not overwhelming or localize-able. Playing the movie clips was when I couldn't get a silly grin off my face! Even giggled out loud a few times.
Everest, the storm arrives scene literally shook my chair & body like never before...I think I have finally experienced the "wobble" effect you all talk about. Felt like my breath was pulsating in and out of my lungs instead of a smooth stream, if that makes sense. And this was at only -10MV (usually listen around -15 to -12).
My first thought after playing with it for a couple hours? "I need 4 or 5 more of these things!"