Andrew,
Are you set on a TV or are you considering projection? Not that it matters to where you mount your surrounds, but it will matter to what wire you will need to pull before the rock goes up.
Personally I would run conduit for all possible options. It’s easier to not use it than to want it after the fact. A lot of folks (the vast majority) just staple wire. I try to convince them to run conduit, but they usually don’t. I’ll suggest the same to you. It’s easy, cheap and fast and you will always be able to pull in new or different wire as needed. I would run 1.5” or larger to a future (used or not used) location for the projector in the ceiling, and run ¾ to all the possible speaker locations. No need to run rigid conduit either. Non-metallic flexible conduit it what I’d use. It’s commonly referred to as “smurf tube” by tradesmen. You cut it with a pocket knife and all the boxes use snap connections.
Regardless to whether you run conduit or not, I’d still get wires in the walls / ceilings to all possible locations. I’d run two separate wires to locations for the center channel. One above the display and one under. I’d run wires for height channels above the display on the front wall and I’d also run wires for width channels, half way between your mains and side surrounds at floor level. You side surrounds, as already mentioned, should be perpendicular to your main listening position up to 15 deg behind. The rears go to the back wall. You surrounds should be between five feet off the floor and the ceiling. You will also want to run coax to several locations throughout the room. You just won’t know where to put the sub till after all your furniture is placed. It’s better to have several jacks to plug into all over the place than to have to run wire under rugs. You may end up wanting to run more than one sub too, and this will help.
Also, make sure you run a dedicated home ran 20 amp circuit to the equipment location. Make sure that either you or your electrical contractor home run this to the panel and do not share a neutral with any other circuit. I would also install a receptacle near the projector. Run the conductors for this receptacle to the equipment receptacle. You can then either tie this receptacle to the same circuit as the 20 amp home ran circuit, or, you can make up a plug and extension cord from this box and plug it into a surge protector or UPS at the equipment location.
