Hey Fritz, I did the same thing: Test drove a Miata, loved it, but realized it was just too cramped for my large-sized frame. Then I test drove a Z3, and forgot all about the Miata! I found a beautiful 2000 Z3 Roadster (2.3) with 77k miles on Ebay for $13,600 (plus truck freight and tax) from a wholesale dealer in TX, and I could not be happier (that's below wholesale, and no dings).
The Z3 is a magical car. I've never had a car that drew so much attention from the opposite sex. The 2000's seem to be a good model year with very few problems, nicer looking rear fenders, better speakers, chrome trim upgrades, etc. Get heated seats - women love 'em and you will too.
If the dealer is sitting on some surplus inventory, you should be able to cut a sweet deal. You might also try Ebay. I bought from Lone Star Cars in Plano, TX, and they were square dealers, no surprises.
Let us know what you end up buying.
R