Well considering what I've seen in homes and the fact that I am getting more and more frustrated with the lack of front-to-back in my 55, I'd be happy with a 120 right now. Eventually however I'd love to have a 180/225 tank. I think it is one of the nicest "reasonable" in-home tank size I've seen.
Was it GaryM? Someone out in the Rochester direction had a 220 or 225 setup as a divider in their kitchen/living room with a central drain to a sump system setup in the basement. The rockwork was really nicely done as well. It was a beautiful tank, unfortunately he had to break it down because he was moving. I came out with the current owner of the tank to see it before it was broke down.
....although, I absolutely LOVE the 1st picture that Kat posted....THAT IS AMAZING!