Nice to see you back, Jordan.
Some pretty good advice from Misfit. I don't think locating the surrounds in either place you are considering would give you BAD results, though I lean toward ceiling mounting them to the side. It just comes down to what you would prefer. I'd wager you'll find people here that have them mounted both ways. I know Daphoid has his ceiling mounted in roughly the same place you propose, and is completely happy.
However, if you're going to mount them on the back wall you might want to move them farther apart so as to get them away from the couch, even if doing so gets the left surround close to the corner. I know that Ray has his on a shelf in the corner aiming out at a 45 degree angle, and is quite satisfied. Experimentation, as Misfit pointed out, will give you a good idea of what will work for you.
