Yes, if buying used you should move up the line if you can. The 802D is much more open in the midrange than the 803D (I have not heard the 800D). Your room is more than big enough. Your biggest room issue may turn out to be left and right balance issues with all the open spaces. Meaning sound stage, bass, and what not may be off center. But if you do not have those issues now... you should not have them later.
Good luck and shoot high.
Good luck and shoot high.