Hi everyone!
Well, I'm completely new to the forums (but not to the site!), and I have a bit of a dilemma for you…
We just bought a house and now have a huge, wonderful, expansive basement, and my husband and I plan to use it for movie/game nights, our computers, etc. The problem is, no couch fits through the stairwell (when you go up the stairs, you end up in a hallway facing a wall – very tight). So, we have this amazing, humongous basement that is being pretty much wasted on two desks and a cat tree. 
My husband is completely and utterly set on a large and curvy sectional sofa, like this one:
It's three pieces, each a little less than the length of a loveseat. I'd like to build it myself, so a plan would be awesome, but in the meantime… Any ideas? We don't want to spend the $3k+ price tag (whenever we've found one, it's been $3k or more and usually needed to be custom-made).
Any help would be grand!
EDIT: Here's a picture with dimensions:
