I am installing a 7.1 system. The room is a 20x15 rectangle shape with the TV on one of the shorter walls and the listening position at the midpoint. The ceiling joist spacing to the sides of the listening area is too small to allow HTR7000s but I could use 650s.

Here are my options:

1. HTR7000s for L/C/R, 650s for sides and rears with sides directly to the left and right of listening position.
2. HTR7000s for L/C/R, 650s for sides directly to the left and right of listening position, and HTR7000s for rears.
3. HTR7000s for all. The sides would still be on the sides but would need to be moved 2.5 feet behind the listening position.

What would be the best option?

You might consider Invisa MPX for side and rear speakers if they're going in the wall. HTR-7000 does not usually fit interior walls as it's too deep. It was designed for ceiling mount.

All would be in the ceiling.

Option 2 looks good for that.

I went ahead and installed 3 HTR7000s as L/C/R in the 7.1 system. Now I need to decide on the remaining speakers.

The room is prewired so everything will be in ceiling.

I think I am limited to using smaller speakers for the SL and SR based on the spacing of the ceiling joists so will probably use 2 650s. I am assuming the orientation of the MPX is important. If I oriented the them with the short end towards the wall (long ends pointing forwards and backwards) then the sound would project forwards and backwards? Would MPXs work oriented like this or would 650s be better? How does the sound from the midrange and tweeter project from the MPX?

For the RL and RR I have more space so I have more options. I could use 650s, HTR7000s pointed towards the middle of the room, or MPXs oriented to point both forwards and backwards (long ends pointing forwards and backwards). What would be the best option here? Are 650s (can point the tweeter but rest of the speaker is not angled) or MPXs (tweeter is not angled but midrange is angled) better? HTR7000s are better than both?

The use the room is a mix of movies and music. For movies I would be seated in the middle. For music it would probably be best to fill up the whole room with music. There is also another room behind the rears open to this room with no walls separating (it would be nice to hear the music in here as well).

Since everything will be in the ceiling, use 7000s for rear and 650s for the sides. It'll sound great and also look more "of a whole" with all round grilles up there.