Peter,
I would definitely go for the M22s in your situation. I also own a pair and listen to CDs and SACDs of "just about everything" like you do (including Metallica). Mine are about 8 to 9 feet away from the listening position and also about 8 feet apart. (My living room is roughly 12' x 13', with the speakers along the 12' wall.)
This past March, I upgraded from Paradigm Monitor 9 speakers, which were very much larger and heftier than the M22s. I was expecting a side-grade (no improvement in performance, just a smaller package), but I ended up with a
much better speaker overall. So many more details came through the M22s than I had ever heard with the Paradigms. In retrospect, the tower speakers were way too big for my room and that could have been a large part of why I wasn't hearing everything I should have.
You say that you're looking for more depth and warmth. The M22s have a very flat frequency response across the board, so that makes them borderline cool with almost no coloration. Thus, they are highly accurate, so when Lars bangs on that darn snare drum, it's going to bite your head off.
In other words, these speakers won't add warmth where none existed before. The speakers really shine with high quality recordings and SACDs are truly impressive on them.
I don't want to make you nervous about high recording quality being a requirement, so I'll tell you that I also play back my MP3 collection through my M22s and the majority of them sound great, too.
