Mounting speakers behind a wall

[brox]

I'm not sure if this is the right forum to ask this question but here is goes.

I have an 8x10 foot storage room behind my home theater screen. I would like to mount my left/center/right speakers in that room firing through a hole in the wall covered by a grill of some kind. This would give me a nice flush look with all of the speakers hidden behind the walls. I will be using traditional sealed speakers, not in wall speakers.

I have some questions:
1. How will having the speaker inside an 8x10 "box" effect the sound?
2. Would it be better to build a sealed box behind the wall to hold each speaker to prevent air from the storage room leaking into the listening area?
3. Would adding a subwoofer in the same manner change anything?

thanks!