Even if I had all the money in the world, I wouldn't get M2s for surround speakers. Talk about overkill.
On this basis of this thread, I've ordered some JBL LSR308s with a pair of Art CleanBox Pro to convert from RCA to XLR. Hope they sound clean!
This way I can use an Oppo BD player as a prepro. Eventually I'll add some 305s to my rear channels and maybe even for heights in an Atmos setup, unless I can get something more convenient. Seems kind of risky to have powered speakers /w amps mounted overhead on the ceiling. What if they fall! Eeeek. Might be smarter to get some passive concentric drivers for those channels. Does JBL make ceiling speakers like that?
Thanks for the tips, I'm really looking forward to owning some horn speakers with a nice and wide sound field. I used to have Klipsch THX 650s but they were too large for my apt and I had amp issues.