Yes the gk 412 is heavy but light for a 412 cabinet, part of the reason I'm looking at a svt 212av is to be able to move up and down stairs without having someone to help me. The 412 is a 4ohm cab as well.
I hear you with the stairs but you'll regret selling that cab someday. Sure its overkill for just about everything but even at sane volumes it still has incredible presence.