Haven't read through all posts but I have the 600 and weight-wise, it is heavy but I have lugged up to fourth floor (and anything below) on apartments as and when required. Don't get me wrong, I'd sooner not and work other ways if possible, but it can be done.
Easy to get on the van, just tilt back, push then when in position just lift. We have one van with a tow bar and we have foldaway ramps for one man loading / unloading.