First, I agree the Four is a bit obsolete. I loved them at the time, and still have two pairs in my basement, but ski on newer stuff.
Second, demo bindings do not necessarily mean beginner rental skis. A lot of shops put demo bindings on most or all of their demo skis. In fact, I just skied Volk Katanas with demo bindings the day before yesterday.
A couple years ago I had a good experience buying former demos online. You need an established place with a grading system (i.e., if all their skis are graded A+, don't believe it. If the same place has some other skis that are B's, that adds credibility in my opinion.) The other good thing is when they have detailed pictures of the actual skis, vs stock photos of the type.