5.1 vs 7.1 question

[shane1337]

I am in the market for a new sound system for my home theater in the $1,000 to $1,500 range and I am hoping someone can give some insight to dolby 7.1.

My home theater room is about 13 feet by 22 feet, and there is a good amount of room behind the seating to position the speakers in a 7.1 setup, but since all movies are essentially 5.1, is there a notable improvement from having the extra channels?

Specifically I am looking at this system from sony: http://bit.ly/1nIZTn It appears to give the most bang for the buck, but does not dolby hd or newer technologies. On the pro side it is a 7.2 system (which brings me back to my original question) and it has support for a second sub-amp, which I would probably use for shakers (http://bit.ly/aVeqt X 2 in series to make 8 ohms).

Any suggestions or recommendations to other systems in my price range would be greatly appreciated.

Thanks