willmc23,
I owned an MJ Pro 100 for a while. The reason I say "a while" was due to it's size. Before owning a Pro 100 I had the little Pro 50. That was great for my HiFi use but I wanted more headroom over the Pro 50.
The Pro 100 had more power but an identical driver type to the Pro 50, the sound was predicatably very much the same only louder. I chose to try a different manufacturer for my 3rd subwoofer.
The Pro 100 wasn't a sub I really tried with Movies, which is what you're after. I can say though, that if you crank it up it performs quite well, if you pop your head near the bottom (it being downward firing and all) you can feel the air moving.
I have received a BK Elctronics XLS200 in the last 2 days, which "binbag" recommends. I have not had long enough to play with it enough yet but like it so far. It is an IDEAL size for my HiFi area - a bedroom and so great for small area's. This is not to suggest it cannot cope in a larger space.
It looks very smart in silver and I can take the grill off the front and see the chunky 10" peerless driver, if I feel like it. I intend to leave it on though (for protection).
I chose this model after a fair bit of reseach. I nearly went for a second hand REL Q200 (well Q201e as it was the slightly modified version of the Q200 - i.e. it has a grill!). Reading through this forum suggests that the BK XLS200 can be considered roughly equal in performance to the REL, apparently. Not actually heard the REL myself so I cannot confirm from first hand experience. Anyway...
the BK sub is pleasing me with music and it's still being very much run-in. I am not running it past 50% yet on the gain/volume (low level connection). Not thraping my amp either, so it's still playing fairly quietly until I turn up both my amp (increasing the signal it gets) and the sub gain.
I would search this forum for the BK XLS200, as it seems users here have found it performs well with A/V use in surround sound as well as with HiFi. This subwoofer forum has the BK elec advert which links to there site, go check it out!
You need to really consider if you can happily accomodate the larger Pro 100. Make a mock up in cardboard or at least tape out the floor area it would take up before purchasing. I would have probably kept the Pro 100 if it didn't dominate my room. It IS longer/wider than 2 MJ Pro 50's stuck together btw.
Bear in mind that even this larger MJ acoustic offering isn't by any means vast compared with say, a BK Monolith or SVS monster and so on. If you can go big, it'll probably prove better for movies. If you can go big, go bigger than the Pro 100. I say this because if you are directly comparing the MJ Pro 100 vs a smaller sub, remember that the 100 isn't that powerful.
It'll dominate your room more and not necessarily provide much, if any (?) of a performance advantage over a smaller sub.
The XLS200 is very compact and uses a 275 Watt RMS amplifier panel. The Pro 100 uses a 100W version but has twin 8" driver vs XLS having one 10". Remember though, that amplifier power is NOT a definitive answer. Suffice to say, more power is not the only important thing as different subs seem to utilise the power differently. Depends on cabinet volume, driver size, dynamic headroom, etc. A smaller sub may need more power to get some air moving in the room, espeicially if an infinite baffle design (i.e. no ports).
Don't forget to imagine the sub in 3-D as AV gear in the shops always seems smaller! If I were you, in effect I WAS in your situation, go for a smaller sub like the BK XLS200. I also considered having a downward firing (as with the MJ's I had before) VS Front-Firing. It seems in the case of BK at least they perform to the same standards. Howeer in my bedroom, with wooden floor boards, I feel I can better suit the Front Firing sub to the room.
This may cause some debate, as you can put subs on a base like granite or something and reduce vibrations THROUGH the floor instead of pressurising the room with the sub driving 'acoustic air' as it's suposed to (if there is such a thing?)
Good luck
~ mrdark8