Another thing to consider in the "real world" department is that it's not always easy to seamlessly integrate a sub with bookshelves. Sounds like you had a very good setup and experience with the M20s and a sub, but I know in my A/B comparisons of my M30s with sub vs. my M60s by themselves, I always prefer (on music, not HT) listening to the larger speaker that gets a fuller bass range integrated into it, vs the bookshelf with a sub. Some of that no doubt is because I suck at integrating subs and speakers. But then again, many of us do! So it can often be an easier way to get great musicality if you go with a larger speaker for music and forgo the sub.
"These go to eleven."