What size tank?

[Seriak]

Okay, I have one of those new houses with the stairs to the basement that wind down. What is the maximum sized tank that people have gotten down stair cases like this. I would like 6' but I really dont think it will fit. Has anyone had any experience with larger tanks and stair cases like this. My only other options are to buy a new house or have it built in my basement. Both of which cost quite a bit.

Any ideas?