We're back with an update. House is finished, we moved in just before New Year's Eve, and I have some time again now to work on the theater.
I put in the floor, (nearly) finished the Volt-8's, and built a test setup to check the speakers, amp, projector etc. Image and sound is amazing already at this moment, very happy with the choices I made so far. Bad news is that the we weren't able to get the old sofa upstairs, so we had to scrap it. Good news is that I'm looking now to order 2 real home theater seats.
Next up is building the extremely minimalistic false wall and the DIY screen. Once I'm happy with the viewing distance, I will fix the Atmos speaker positions.
My plans for the screen also changed.: I will go for a 116" scope screen, instead of 128" because of the height limitations. I feel the 128" is too low on the wall and will feel awkward. To compensate for the reduced viewing angle, I moved the seats closer, which should give the same immersion and viewing experience.
Back wall will also be moved closer to the seats. We decided we wanted more storage space in the attic, and it allows me to position the 2 subs more ideally so I can sit exactly in the center. Subs will most probably be the Devastator 21" HCR.