While the Camaro is 'heavy'.. it doesn't feel as heavy as an Audi S4..
That's surprising. I've got a VW GTI now, and I'd have expected the Audi to be closer in feel to that than the Camaro. Part of what bugs me about most American cars these days is the high beltline -- it feels like you're sitting in the bottom of a bathtub.
The M3 actually sounds like a lot of fun, or maybe a C63 AMG? ;-)
What about a WRX? Could be a different sort of fun altogether. I didn't see any drop-tops in your list, so I assume the Boxter is out? Audi TT? 370Z?
Lots of fun choices in that price range. I think I'd plan on taking a *lot* of test drives.