I actually bought the 5Bs before upgrading to the 4Ts, I had the same plan of wall mounting them. I later realized though that by the time I buy the mounts (or stands) the total cost is pretty close to that of the 4Ts. So may as well put the additional money towards better speakers rather than furniture. The 4Ts offer much better mids & a much larger sound stage.

Since your room is a  good deal larger than mine, and you will be losing the sub, I would go with the 5Ts should you choose that route. Although, if you go with the 5Bs you can keep the sub which is likely to better suite you since you said you're primarily watching tv/movies and not listening to much music which is where to towers really shine.

Also, you may want to look at the 5C rather than 4C. I recall reading somewhere that the 4C is recommended for sitting distances of up to 10'. Plus the 5C's frequency response is awesome for both movies & music.

The gurus will be around tomorrow & will be able to offer better advice than me of course though I hope I'm of some help.