I use a pair of M106 for our home theater/music listening space. Our space is a 14' w x 12' deep end of our finished basement. The ceiling is 8' high.
The speakers are about 9ft apart, 18" from the front wall. We sit about 8.5 from the screen. We rarely push our volume over -70-75db. I'd say our sweet spot -65db-70db. After that it just gets REALLY loud. We don't use a center - much prefer the phantom center set-up - as our space feels like it's the perfect set-up to take advantage of this.
I push the speakers with the Denon x2600H. We have Revel M8 on-wall speakers for surrounds. I absolutely love this rig. It gives us a solid cinematic experience for such a small space. The waveguides on the M106 certainly help. We have no side-wall nor ceiling treatment. We have a thick rug and rug pad on the floor, and a big fabric covered sectional.
In a more comparative set-up (bookshelves vs. floors) regarding the same space to what you're considering:
Previous rig:
Polk LSi15 towers L/R, Polk LSiC (center)
New rig:
Revel M16 bookshelf L/R, Revel C205 (center) - replacing the Polks
This is also used for movies and music, but it's in our living room (22' x 16' with 18' ceiling). The sound is greatly improved in terms of clarity, especially with dialogue. Volume? The Revels have zero issue competing or matching the Polk LSi speakers. ...We push the volume upwards of 70-75db here as well. If you need more volume, I can't say how well it holds up, as we don't push it past -80db. But we don't sit a long distance from the speakers either.
The Revel C205 a big upgrade over the Polk LSiC - especially in clarity and definition when it comes to dialogue. I prefer the phantom center in our HT set-up in the basement over either.
As for filling the space with sound, the M16 bookshelf has zero issues. ...I chose the M16 speakers over the KEF R3, the latter which I found quickly fatiguing (personal issue).
All the Revels (M16 and M106 speakers) seem to be on sale, including the Revel C205 - so it's hard to not recommend this right now. ...you also have a 60 in-home trial period through Crutchfield, so you can always buy-n-try (live with the speakers for a while), and switch if you don't like your choice.