Hi Bill. Welcome! Well, bookshelves with a sub (depending on the sub) should go lower in frequency response than floorstanders, such as the M60s, by themselves. The question is, how deep in the frequency response does the music itself go? There are some who feel that very little music goes much deeper than what the M60s and M80s offer. Unless you already have some, don't forget to factor in the cost of stands for the bookshelves. Stands are superior to placing them on shelves, etc. due to the effect of the shelves on the speaker's sound.
I am a happy M60 owner. But If I could only have the M60s alone, or M22s with a sub, I think I'd go for the M22s and sub. Now if you could afford M60s AND a sub, that's a horse of a different color.
