ARC LS25 pre------>
NHT X-2 active x-over (low-cut filters the main signal)
High pass from X2---->ARC VT130SE---->MMGs
Low pass from X2---->Velodyne SMS-1--->2 x Rythmik 12" subs
(SMS performs digital room correction + high cuts bass signal)
NHT X2 =$300
Velo SMS-1 =$400
MMG = $600 (when I bought 'em)
Rythnik subs 2x$800 = $1600
Total budget = $2900 for full range, room corrected bass with planar response from 75hz on up. Some won't like the idea of the NHT X2 in the main path, but it's really benign (to my ear, anyway). The SMS-1 (or, I'd guess, the SVS Audyssey unit) are almost mandatory IMHO for best results. They smooth the bass response of the subs and allow you to fine tune the "hand-off" so that it's seamless.
This is probably the best bang for the buck full-range system that I've ever heard. I also use Ohm 100s in lieu of the MMGs because the I like the omni dispersion, but that's personal taste and another $1K on the price tag.
Good Luck.
Marty
BTW - I cross at 75 hz because that's where my passive treatments (bass busters) cease to be effective. YMMV on that one. However, my MMGs operated full range (no subs) started to roll off in the high 50hz range and dropped off very sharply at just under 50hz (per the readout from the SMS-1 real time analyzer). Again, in your room, MMV, but don't count on anything approaching 30hz.
As to max SPLs, I've got more than I need with this set-up. However, I've never tried to see where the MMG maxes out on its own, so I can't speak to that one.