Just uploaded the pic. Thanks to Rivernugget. The backwall is a little short and why I was thinking to go in-ceiling to "cover" more area. After seeing your post, I am doubtful it IS the right decision/direction. The other direction is to go for in-wall for rear. Limitations are first the people sit on the side might not hear the rear speakers that well and the speakers will be just behind the ears for the people facing the TV...maybe it is good thing? I assume light of sight for speakers, maybe it is not right with klipsch speakers... i.e they might have pretty front distribution even for the direction not facing them directly?
Somehow for the front and center, I am reasonably sure we will get seperate systems. Coytee, I do agree if the burried type, we will go for the in-wall for sure. Maybe the safe thing to do there is to ask them prewire the front and center in-wall at 4' then they can either for external or for in-wall later. Thanks everyone for the feedback again.