The M2 was developed with music in mind and is used by professional recording, mixing and mastering engineers. It is a professional full range monitor that many consider to be one of the finest. It is an excellent speaker for music and Home Theater.
Why do you want to use 2.1 for music if you still want to be able to do TV/movies? Phantom center is not ideal. You will be missing the center channel and surrounds. I was stuck with 3.0 for a long time and am finally able to have 5.2 again. I really missed having surrounds and could not imagine not having a center channel for TV/movies. Dr. Toole says not using a center actually diminishes dialogue clarity. The most prominent thing in TV and film mixes is dialog. I listen to music in both stereo and surround and enjoy surround for TV/movies. You say "2.1". Most HT designers recommend at least two subs these days; it helps smooth out bass response in the room. Have you read Dr. Toole's book or the information on the companion website?
https://routledgetextbooks.com/textbooks/9781138921368/
You can control M2's with some Crown amps or use a BSS and any amps. You need one or the other because the M2 anechoic data is in them. Most Crown/JBL Synthesis amps for the M2 have noisy fans. People choose to use the BSS if they don't have an equipment room for the amp. If you have to locate the amp in a remote location, you have long speaker cable runs.
Your sources (Apple TV and Blu-ray) feed the preamp so you need to consider how that will be accomplished (are there HDMI inputs on the preamp?). The output of the preamp feeds the BSS that feeds the amps. M2's are passive and require active bi-amping, BSS or amps control processing and crossover functions. Two channels of amp are required for each speaker (woofer and compression driver). Placing M2's in a cabinet is not ideal. You might consider using SCL-2's (designed to be in wall speakers). M2s were engineered to be used in 2 pi or 4 pi space, where the SCL2 was designed to be used in a wall. They have crossovers built in and would make your setup much easier by eliminating the need for the BSS processor/crossover and four channels of power amp vs. two. https://trueaudio.com/st_spcs1.htm
Not sure why you are building things into a cabinet. They are not ideal for audio reproduction and can limit your ability to grow/expand. I have a friend who did one a few years ago. He wanted to get a bigger center channel recently but can't. What if you want a bigger TV down the line? How big is the cabinet and what size TV will it accommodate? Could you elaborate on or show drawings/pictures of your "cabinet"? An empty box cabinet is a nightmare for sound.
Have you considered Revel vs the M2 and have you seen the thread that compares them?
https://www.avsforum.com/forum/89-s...iewed-speakers-ever-made-14.html#post54632024
John Schuermann says, after many hours comparing SCLs to M2s to Revels he finds the SCL / M2 speakers have more prominent direct sound and sound “drier” than the Revels. Revels sound silkier, smoother on the top end vs. the JBLs. The SCL2s sound more spacious than the M2s, likely due to the waveguide design. He likes how close mic’d brass and percussion sound with the JBLs, but prefers everything else on the Salon2s. The SCL2s sound more spacious and open than the M2s, but aren’t full range down to 20 Hz, which is not and issue if you are using subs. The second most prominent thing after dialogue in any film mix is music.
FWIW, setting up M2s is complex and may be beyond what you want to deal with.