I upgraded from the LFM-1 Plus. I tried to keep both, but my better half wasn't having it. The X12 is only slightly bigger than the Plus.
I could immediately hear a difference in how the X12 reproduced a much more precise sound. Especially noticeable at the lower end compared with the Plus.
One of the first movies I played was the "Edge of Tomorrow" opening scene where the bass starts out as low as any movie I can think of. The X12 reproduced this without any problem. The sound was quite crisp and impressed me in that it never bottomed out, whereas, the Plus struggled a bit.

The bass reproduction of the X12 is definitely an upgrade over its predecessor and is doing well pressurizing my room.
I'm using it in bass extension mode, with one port plugged for both movies and music as I think it sounds better to me in that mode, for either.