I agree with what everyone else has said, go bigger than you think you will need. Where do you sandwich your quilts? Will you have an area large enough to do that? If not, make sure you have enough open space to lay out the project on the floor. LOVE the idea of hanging the batting close to a cutting table! Storage...Storage...Storage! Also, love the idea of having some non-sewing furniture so if someone comes in they have someplace to sit.
Good luck. We'd love to see pictures of what you decided to do.