If you run the in-ceiling speaker wires for the rear speakers, and you don't use them, it won't be a big loss. I suggest you do that and agree with a 5.1 system. It looks like a difficult space for it though. Have the 2 surround speakers there in case. The 3 front speakers don't need prewiring. You need to decide between a 2 channel system and 5.1 at this point because the electronics you buy will dictate this. You can try 2 speakers and see if you like it in the space. If you want more, just hook up the rear in ceiling surrounds and a center channel at a later date.. If you decide anything higher than 2 channel, it might as well be 11 channel. That's just how the AV receivers come now.
I have a 5.1 system and enjoy it very much. I also have in ceiling surround speakers but I have 8 foot ceilings.
I have a 5.1 system and enjoy it very much. I also have in ceiling surround speakers but I have 8 foot ceilings.