I think a psychological evaluation test would be a quite high hurdle (for customers but also for the company regarding privacy and an immense workload, how to keep the questionaire secret, do you change it regularly to insure unbiased answers, it would be endlessly long, laced with control questions etc.) and send a very difficult message. It would probably be a feast for the mINdConTrol crowd. Maybe it could work for a voucher, but most problems would stand.
Probably best to start with the data at hand:
How long is he/she customer? How many products purchased? Maybe different categories would help: X number of “beginner” subs (LBfH, AC, Genesis line) purchased, Y number of experienced user subs (Emperor etc.), Z number of artesin titles purchased.
Maybe a small points based system would make sense?