A/C is expensive to add to these cars because they really don't have a lot of space and it's mostly labor to make it all work cleanly.
Of your options the roadster with a really nice hard top is likely the best all around option and also fits your price target (new or used). As for the price differences among makes, unless you experience them all in person both driving and appearance there's no easy way to gauge the differences. All I can say to that is they all seem to sell quite well to a long list of happy owners...
I'm trying to include some pictures of the new "Fastback" roof from Backdraft. It comes with different side options such as a scoop, a window, or blank.
