Not to question your spatial ability- but I worked as a mover for a few years and found there were almost no instances where we couldn’t get a couch through a door. The only ones that are a complete loss are basement apartments where there is a wall on both sides of the door that doesn’t allow you to put the couch on it’s end and kick the bottom out allowing you to thread the couch through the opening on an upright angle. If you have enough room on both sides of the door to rotate the couch while standing on end, you should be able to do it. If not, then, yeah, the window might be the only option. Depending on how high the window is and your relative handiness, there are a variety of fun lifting devices that you can get from the rental shops….Might be cheaper than the movers.