Most any sub that is clean and accurate, in other words good for music, will be a decent combo with the maggies (I have 1.6s).

The cleaner you can make it, the better. An IB would be the ultimate for blending, followed by dipole woofers, then sealed, then a PR or ported unit.

Obviously there is some overlap amongst different sub alignments, where a really good implementation of one type might be better than another that normally performs a little cleaner, all other things being equal.

I have some dipole subs XOed to my 1.6s, but then also have a pair of big ported subs for the whole system. When listening to music, I treat the 1.6s as full range since with the woofs they are flat to 25, and basically go down to 20 in room. I use the subs for mch music for the .1, and run all the maggies in the system as small for movies, games, etc. with the big subs covering from 80 down (higher for my maggie surrounds).

My big subs are a pretty decent ported design, but there is a pretty noticeable improvement going to the dipoles on music.

My dad has the LFM-1, and it is indeed a very decent ported sub. If you are looking for anything below 20hz, you are likely to have to go ported unless you have some flexibility in the areas of an IB, or big boxes, or big $$$.