Actually, when I was looking for (and then bidding on) a machine, I asked Billy (Lostn51) to give me some feedback on what I was looking at. He's an amazing resource, and has a good idea about the old machines.
For my money, the new machines have nothing on the old ones. If you want a powerhouse, go for an old metal, mechanical machine. I love my new Juki, in part because it is like the oldies- just oil her up and she'll go.
Ask Billy to take a look at what you are considering. you can just cut and past the ebay links into a PM. He's great.