Be careful what you wish for.....
When you get one Kirby, they have a tendency to sneak up on ya awfully quick, and then next thing you know you'll have TONS of them!
There is a few differences here & there between the older models, but not much. The 50's & 60's models, such as my Kirby 519, are lighter to push than say a Heritage or Classic III. I would start with a 500 series model if I was you....just a thought.