Why is an XA30.5 a bad match for Revel Ultima Salon II speakers?

Thanks for the lengthy reponse Bombaywalla!

Most of my daytime listening is around 80db to 85db according to my ratshack meter's C weighted average mode. I really have no idea what the true peaks would be. I think most music I listen to wouldn't have anything too extreme. Listening to the 1812 overture is a compromise though... I like to turn that up so that I can hear the quiet passages, but my amp is running out of steam for the canon shots.

Having realistic playback levels sounds like a worthy goal, but to give you an idea about my hearing sensitivity, I often wear musician earplugs to play my grand piano because it's too loud for me.

I feel like my system is most coherent and enjoyable at the 80ish db level. Brass and other instruments are really vibrant, and even startling at low volumes.  I'm not sure if that's primarily because the amp has an abundance of headroom at this level,  because the room gets overloaded with slap echo and wall vibration at higher volume, because humans have a different hearing response curve at different volumes, or if it's a combination of all three or other factors. I'm really pleased that my system sounds very dynamic to me even at 70db, and my fiance probably appreciates that at 2am even more than me.

Do you think the dynamics would take a turn for the worse at 80db in comparison to my current M106 speakers?

Is it harder for an amp to send a 25hz signal to a small speaker like the M106 that can't reproduce that, or a speaker that can? Does the crossover actually trim that out of the small speaker and make it easier?

here is a link to the imp & phase plots for your Revel M106 stand mounts:
http://www.stereophile.com/content/revel-performa3-m106-loudspeaker-measurements#ljf3ojqamBz1KzED.97

tough imp & phase plots once again...
And, here is a synopsis of its specs:

http://www.stereophile.com/content/revel-performa3-m106-loudspeaker-specifications#usPtaevBJxpkUyqE.97

with a -3dB at 59Hz, it's easy to see why the 1812 Overture canons are lacking. Your stand mounts just don't have the capacity to reproduce such a low freq. When we say -3dB at 59Hz the SPL/volume is half (-3dB) at 59Hz. The SPL is probably back to 100% at a much higher frequency such as 90-100Hz. So, essentially, you have very bass coming from your M106 speakers & I think you wrote that you use a Velodyne sub - I can see why. 
The XA30.5 "sees" the x-over of the M106 & this x-over is providing a high impedance to the bass frequencies so the XA30.5 is probably sending very little power to those low frequencies. IOW the XA30.5 is probably not taxed much at these low freq due to the M106 design.

For the Ultima Salon II speaker, it's a different ball-game. The -3dB freq is 23Hz & 23Hz is in the deep bass region (unlike the M106). Now the XA30.5 will "see" the Ultima Salon II x-over & this x-over will demand lots of power into these low bass frequencies. I expect the XA30.5 to run much hotter temp wise as it tries to deliver power into these low frequencies & the XA30.5 will get taxed much more than it ever was with the M106.
So, yes, I expect the dynamics to worsen at 80dB SPL with the Ultima Salon II.

One more thing to remember (that many forget) - even if the Ultima Salon II are 23Hz capable, does not mean you will be able to reproduce 23Hz in your room. Based on your room dimensions you will be able to support a certain min frequency.
Here is a room modes calculator that will show you what the min freq your room can support:
http://amroc.andymel.eu/?l=19&w=17&h=9&ft=true&r60=0.6  
 

So in simplest terms, I can think of the impedance curve as an inverse current requirement curve? I can see that the Salon II would take a LOT more juice all the way from 600hz on down, and even more so below 50hz. I can definitely see how any music with significant content in the bass region would demand a lot more from the amp with full range speakers like the Salons.

It looks like even the "friendlier" Wilson Sophia 2 would be a significant increase in workload.

Thanks for helping me understand that!

So in simplest terms, I can think of the impedance curve as an inverse current requirement curve?

yes, in the simplest terms that is correct.

Thanks for helping me understand that!

welcome! glad I could help.

Thanks for the link, it was a nifty tool for discovering I needed to tighten up an air conditioning duct cover when my Salon 2s made it buzz at 20.1 Hz!