Room size

So I'm moving soon, and was wondering what size room I should belooking for which would be reasonable for my system:

anyways, what dimensions do I want and what geometires are absolutly no-no's

thanks for the input, my current room is way way way too small
In my opinion and its only an opinion I would be happy with a room that was in the ball-park of 13x25 or bigger, that way if you go into 6.1 or 7.1 you can be 10 feet or so from the fronts and video with a spacious sound field and then you have plenty of room behind you for the 6th or 7th channel to spread correctly, and as far as room dimension, I would say any room that is longer than wide and the front placed on the short wall would be ideal, just my thoughts though....Chad
To me the important question is how loud do you play and how close do you want to be from the speakers. Moving the speakers out from the back wall you will find the optimum distance for spatial imaging. Then you can determine how far away from the speakers you want to sit. Then determine how far from the back wall you want to sit (not too close). This should help you determine the front to back distance. The length of the front and back walls should not be the same as the sides, or even 1/2 or 1/4 of them, to minimize standing waves and null points. The "perfect" room has all sides unequal and unparallel but of course no house has a room like that. Even with "perfect" dimensions, there will be alot of experimentation and frequency measurements to optimize the sound, but after all, that is part of the interest and fun. Good luck and have fun!