I finished dialing in the subs last night and did some listening. The headroom improvement is quite astonishing.... I actually believe I'm getting close to "enough bass" which is somewhere I never thought I would arrive.
The plan is still to go with the 8MFWs and see how long the Mael will hold together. If it craps out I'll use it passive as a resonator in the wall.
Maybe this weekend I'll shoot some pics of the MaelX under some high excursion, it is quite unreal to see that much woof with that much travel.....
I do like the IB sound though, and If I were to re-do my sub setup I think it would be an IB setup. Easy to power and lots of displacement/extension, best of both worlds IMO.