Greg -
As custom installers, we frequently have to combine room aesthetics with “purist” audio and video considerations. And we’ve worked in your exact situation (TV mounted over a corner fireplace) for a number of clients.
I see three options for you, each with its own pros and cons.
1. Keep the TV where it is, and use in-ceiling speakers for the fronts. These would be arranged in a line parallel to the TV. The surround speakers can be in-ceiling or in-wall (or freestanding, but I’ve never seen a client who wants that). This option provides the best soundstage for the front speakers, and keeps the speakers out of the room. It has several drawbacks, including the difficulty of getting wiring to the right spots in the ceiling and the acoustic concerns raised by arranging the speakers out of alignment with the room.
2. Keep the TV where it is, and use a surround bar for the fronts. Again, you could use in-wall, in-ceiling, on-wall, or freestanding for the surrounds. This option makes your front speaker wiring much easier. And there are many surround bar options that can look good with a wide variety of TVs. Of course, you still have the acoustic concerns, and your fireplace design may not allow for this option.
3. Move the TV to a flat wall, and mount speakers normally. An audio purist would prefer this option, because your speakers are now able to be in the “right” spots in the room acoustically. However, your interior designer would probably have a fit, since you’ve now totally screwed up the room flow and focal points of the room. Where do you put the sofa - looking at the TV, or looking at the fireplace? and you may have issues mounting the speaker that ends up near the corner where the fireplace is (depending on the room).
We’ve used all of these options with various clients, and the end choice usually boils down to this: Which compromises are you most willing to live with?
Good luck with your project!
Rob