"The speakers will be built into the bookshelf with their own wood enclosure matching the shelving. I would also consider a compact bookshelf speaker but my max height is 11 inches and max depth 13 inches icluding cabling."
You need to do some experimenting. Putting a bookshelf speaker in a bookshelf will have a huge impact on how it sounds. I know that sounds silly, but the vast majority of bookshelf speakers were never meant to be put in a bookshelf. Maybe get a cheap pair of Pioneer or Polk from Best Buy just to see what you're getting into. You can always return them, or trade up to the ML in walls you first mentioned.
You need to do some experimenting. Putting a bookshelf speaker in a bookshelf will have a huge impact on how it sounds. I know that sounds silly, but the vast majority of bookshelf speakers were never meant to be put in a bookshelf. Maybe get a cheap pair of Pioneer or Polk from Best Buy just to see what you're getting into. You can always return them, or trade up to the ML in walls you first mentioned.