I'm in the process of developing the basement and a CAD drawing of everything was the best way to ensure accuracy.
The problem with hooking them up in multiple locations is that I want to plan ahead for where the surround jacks are going to be located since I'm running the speaker wire in wall. So while there will be some flexibility to move them after everything is finished, if I don't nail the location first try, it won't look as clean.
The screen and speakers are set out from the wall simply because I want to minimize the distance from the couch to the screen, I know it may sound anal, but THX/Dolby standards state that for a 50" screen, the viewing distance should be something on the order of 7' or so and thus until I can get a projector up and running, this is the best compromise.
Since it's new construction, a shade will have to be purchased for the window, but it's something that will be properly colored for the space (dark) and often left closed, but yes, climbing on the couch to operate it will be neccessary.
In continuing my research on the matter, I came across some literature (page 6) about the effects on mounting bipoles on the side walls, too close to the rear wall (which it would have to be in this case, else mount the speakers ahead of the listener) and how that can cause excessive sound reflections.
Frustratingly enough, the only bit of information I can find on actually corner mounting them is in this thread where a Klipsch employee states:
...with respect to mounting RS-52s.