7 walls? is that all you have to deal with??
Ribbing you. You would NEED to be a mathematician/engineer to fine tune those frequency waves!
AS posted earlier, I used the M3TMs ins a 13x17' listening room with another leg shooting off to where my bed was.
1. I found that using a faux-barrier on the side of the room towards the bed was able to make better balance b/w L and R channels b/c of matching the bouncing of sound waves on both sides of the speaker. You can use furniture, audiophile barriers to do this with pretty good results.
2. If you may be moving to a smaller space eventually, IMO, I would just get the smaller M4TMs and add one subwoofer, IME, you would not need 2 subs. And this is coming from a person who absolutely loves bass. Im not a basshead (my def: so much bass that it detracts from the SQ of the mids and highs), but bass is critical for me. not just for pace/rhythm, but for "fill". meaning that it is that little extra bass that goes down to 32 hz or so. It just gives me that little extra feeling of live
music, or presence
of the musicians in the room. You have a big room, and IME, would be fine with one sub in the center b/w your speakers (that is what I prefer).
3. the sweet spot for Spatials has historically been relatively narrow. That is much better these days with Spatial, but still has a focussed spot of best SQ in the triangle setup of speakers and listener. I still found that when I had music playing and was wondering around the room, the SQ was still very good, didn't feel like I was missing anything.
4. Although the Spatials have triode, easier to drive drivers, they still require a bit of power to make them sing.
People use all amps: tubes, SS, class D with good results. But if you run it with tubes, you will need some decent tube power. Class D amps really play well with Spatials. or a hybrid system (like the famous Vinnie Rossi amps that Clayton often uses at trade shows) are great.
5. Feel free to call Clayton in Utah. He is very personable and happy to help. I bought my M3TMs directly from him at a trade show in CA .... at a discount.
In fact, now is the best time to reach out to him. the big AXPONA show just ended 2 days ago, and all those dealers at the show now have Demo equipment on their hands that they want to get rid of. This is a strategy I have used over the years to get basically new gear for a discount. And they've already been burned in for me
best of luck