Steve, welcome. One significant factor that you didn't mention is the position of the couch. If it's almost at the back wall, along with the horizontal part of the sectional, you'd be around 13-14' from the screen and front speakers, and it'd be a good idea to have the mains separated as widely as you could.
Placement on the bookcase shelves wouldn't necessarily create any problems. The speakers shouldn't be recessed into the bookcase, but should have the front edge protruding a little(say 1/2"), to minimize reflections and refractions from the surface of the bookcase. As long as there's at least a couple inches open behind the speaker, that's enough "breathing room" for the rear ports.
If you're going to stay with the bookshelves, the question would be is there enough room to place a M22 vertically. Subject to available room, my thought is to get M22 mains and a vertical M2 center. This would also be less costly than the list you propose.
