The couch is a large, L-shaped sectional and will be about a foot away from the left wall, and a foot away from the back wall which does put it about 13/14ft away from where the speakers will be going. The bookcases can't be moved unfortunately. I've tried sticking some speakers in the book case and immediately got a weird boomy sound, so it's looking like that option is out.

A vertical center is a good idea, but it won't work for our room. The center speaker will end up in front of the fireplace on the center of the small concrete shelf and can't be too tall or it will block that. Looks like I'm down to two options . . . put the mains is on either side of the concrete shelf (limited L/R audio field but I can get larger bookshelfs like the M22s) or put the M3s on top of my book cases and have the tweeters nowhere near ear level (but much wider apart).

Hmm, two people and two recommendations for the M22s over the M3s so far. Are they a noticeably better speaker?

Thanks for all of your help!