Tyson, good luck with you project. For what it is worth, I think we're on the same wavelength in regards to taste in "slam" in the lower mids. The only planar type speakers I've heard that came close for me in that regard were the big King Electrostats, and even those (in this specific regard) were not even close to a match for even my cobbled together Super-V coaxes in open air.
The LS-X with the Doddzillas were in the ballpark, but lost that specific "brand" of magic for me when the battery amps got switched in. I only heard the S-7's with the battery amps, so maybe just a tube rolling exercise or maybe they just need more power to sing like I like? This fine point is really one of my personal moving targets for "greatest speaker EVAR!" After playing with the V's, and hearing a demo of the bigger BMS coaxials, and hearing AJ's 1812, I think this specific point is something that the big pro-sound drivers just do "right".
Danny, if you're still working on the Serenity Line Force, please do whatever you have to do (stack a couple prebuilt doubles on end or whatever) to try them out with an array of six servo 12's on a side. I mean what I said last year with the LS-X's; I really think getting a line-source wave launch nearing matched sensitivity from the bass modules (and the associated increase in headroom with the same powered servo amps) needs to happen to get the whole speaker "there". At the price point the Line Force will likely take up, half a dozen servo drivers and an upgrade to the big dual channel amps I don't really think is too far a stretch for the reward.