I'll be facing a somewhat similar issue in a month or two when I move a 300-lb 16x24 laser from the garage down to my basement office. I'd originally planned to use a stair stepper like this one and move it myself:
https://www.youtube.com/watch?v=ifWSXhCJFkE
Googling for "stair climbing dolly" should turn up quite a few brands and more detailed searches should turn up some local rental place that can provide by the day or for a 4-hour rental. Here in the Chicago suburbs, there are several rentals within an hour's drive that will rent for $100-200 per day.
Due to some recent back problems I will probably hire some help and let them do the job with the rental unit.
In past years my wife and I moved an 1,100-lb Tormach CNC milling machine down to our townhome basement (in pieces) and a couple years ago I moved a 1600-lb Tormach lathe (also in pieces) down there with the help of a couple paid helpers. We just needed them for the lathe base which weighed over 400 lbs. I'd have been tempted to try the rental stair climbing dolly on the lathe myself on both tools had I been aware of local rentals at the time.
Here's a narrative on the mill move from about 9 years ago in case anyone is interested:
http://memweb.newsguy.com/~mphenry/t...isassembly.htm
We used a crude A-frame supported against the basement doorway and a Harbor Freight winch to lower some of the heavier mill components and the lathe bed down the stairs and that worked pretty well (see the pictures about 2/3rds way down the above link). I still think that the stair climbing dolly is a better solution, though.
