Used Cirrus values were bound to bomb because a) Cirrus was marketing them like cars so they were bound to shift a fair # of them to people who then "discovered" that the despatch rate of an SEP is not quite the same as the despatch rate of a car, and b) the regular technical upgrades made the "old" versions less desirable.
The advertising style was IMHO essential to break the "GA anorak" mould. The innovation was also something to be pleased about but ultimately it was going to catch up with them by saturating what is a pretty well limited market.