You pulled the trigger on the 800 already so there isn't any real reason to comment, but I'll concur with the majority of the opinions here. IMO, decent subs aren't just a recommendation for a true home theater, they are a requirement. Towers that can play down to the 30's might be good enough for playing music without a sub, but will not do justice to explosions, rocket takeoffs, earthquakes, or any other movie scenes where frequencies around 10hz or sometimes even lower are produced.
First movie that comes to mind for showing the real advantage of a dedicated sub is Cloverfield. There are many scenes in that movies with single digit frequencies. Find me a tower speaker that can play those scenes as good as a 12" or 15" (or larger) sub and I'll eat crow.
Here are some graphs of several bass heavy moments from that movie:
http://www.hometheatershack.com/forums/databass-movies-deep-bass-dmdb/18500-cloverfield.html
