I built a HT closet and placed my EP800 inside of it facing out. While it worked, it sounded amazing. However, I did notice when I went inside the closet that there was a lot of bass that eminated from the rear of the subwoofer (even though it's a sealed box) that was getting trapped inside the closet. Since it stopped working before I ever got a chance to bring it outside of the closet to play around with placement, I can't say whether or not it made a huge impact or not.
It did still sound incredible, I'll say that. So I would say it if it's a must for WAF, then don't be too scared to do it. While it may not be ideal, it will still probably be acceptable.