Listening/viewing area is 18 x 12. Room does extend another 18 to 20 feet though.
The heights add ambience but the cost goes into what we call diminishing returns. I wouldn't do it again until BD movies go beyond 7.1 with the sound effects.
I've spent some time with the DF ST-L speakers and they are definitely hitting the spot--a perfect match for my SC8000 and Mythos Ten (Center/Front L/R-High) 7.1 home theater. Great packaging too--it arrived in perfect condition. Setup was easy and the sound is mighty impressive.
This setup is in the informal living room and I went with consumer grade components; which seem to be working out quite well.