I’m a german car guy and I’d tell you to buy the C5, or an S54 M Roadster (unless you plan on going turbo, then get the S52).
M roadster looks like the ambiguously gay duos car.
Honda S2000, thank me later 
maybe boxter maybe vette maybe convertible maybe hardtop,
wheel burning beast v8 or sexy curvs and neutral handling of boxter but since only 20k boxter no S is really slow, dads friend had one use to drive it alot 99 my 92 C4 would eat that german bettle with no top
dont get me wrong my fav car is 911 to the core, but everything, looks power price performance maybe even looks would be vette , why not forget about gas:pimp: and think about smoke, V8
GO VETTE no doubt.
the vette gets em wet.
Pat Leary on Union and Clinton has a Z3 i know its no ///M but its also somethin tho think about…they do have a stook also…my personal choice would be the poor mans 911 aka Boxster
:word: i went by there yesterday and they now have a 06 sti on the lot as well
wow. hard choice.
Boxster S FTW
I’d probably go with that, but it also depends on how much you want to spend for maintenance…
i would get the porsche, it may not be really fast, but its definitely fun car to drive,
Get the Mustarang.
Something you didn’t mention… miles. I mean, you can find some amazing cars for $20k, but they may have 80000 miles on them. If you’re going to spend 20k, and finance it for probably 48+ months, you don’t want something with a lot of miles.
A 1997 Boxter with 50000 miles is going to be a 13 year old car with about 100000 miles on it by the time you’re done with 48 months of payments. (a little over 12k a year).