I recently purchased from Frank Nutt's a Bernina 457QE which is a slightly smaller version of the 740, not having the 9mm stitch width. I am very impressed with it, simple to use, stitch quality great and the super sized bobbins are fantastic!
If I had the money at the time, I would have gone for 7 series, but they are pretty large, and would not have fitted in my elderly, but very useful Horn cabinet.
Bernina feet, although expensive are a work of art, but I imagine you would get all you would ever need with the 7 series!
However, I did have the original Pfaff Passport some years ago, which I stupidly traded in, and wished I hadn't!