Just wanted to close the loop on this thread... ended up with an E90 M3 after MUCH thought. Couldn't be happier! As such, the S2000 is up for sale--wish I could keep both, but it's just not in the cards right now. So! If anyone's interested in a low-mileage S2000...
Thanks again for everyone's input, thoughts, comments, and advice. M3post sure is a great community!