I have considered other Martin Logans--they seem a tad expensive, given the use is basically just going to be Atmos. I'll look further into the RSL c34s. Out of curiosity, can you angle them once they are installed or are they just going to whichever way they're pointing? (Not a big deal either way, just curious)
As for as the MLP, it will not be against the wall, but not quite in the center of the room. So, we're looking at the front in ceilings being a bit further in front of the sofa then the rears will be behind (about a foot each way, so maybe two feet further away). I'm open to considering just two instead of four, although the price of installation (I am, alas, not a DIYer, or at least, not to this extent...) will be not that different so I figured why not put them all in.
(And as for rotating, that was always what I wanted to do but for various reasons not relevant here, just never worked out as an option, so I have to make do.)
Again, many thanks for all the replies.