Yes, three of the same speaker is preferred, if you can get away with it -with an AT screen you have that opportunity. I'd keep all 3 m60's at the same level and angle. You can probably split the difference between the height of the first and second row for tweeter position, but I'd focus on the front row. One gets used to the sound, regardless of seating position, pretty quickly; even IMAX theaters don't have their tweeters aimed at every seat.

Scott

My HT