Hey everyone, thanks a ton for the useful suggestions! To answer a few questions my TV will most likely be mounted on the wall, but I will still have a cabinet for storage which can hold the TV if I change my mind before the room is built.
The other thing is I have a sliding door at the front corner of the room which really means I can't put standing speakers or the lounge there. That was my initial consideration for in walls. As that wall beside the door is where the TV will mount and I figured two speakers either side and one below it plus my rears behind the lounge would do well.
The other problem I have is nowhere in the area has Klipsch speakers (I can get them through our local supplier though) so I can't sample the various in wall or free standing speakers to see what would be good. Any suggestions on models?
Also I know that I will lose some sound quality with in walls as opposed to free standing beasts, but considering I've been only using TV speakers for my whole life, I think this will be a considerable upgrade!