Since you are looking at a Porsche or Audi, I doubt my suggestion will hold water, but if it was me, I'd buy the top of the range Mazda MX-5 - which is probably the roadster coupe.
Parts are easy to get and the build quality is good.
Compared to a Porsche, my old mazda Eunos doesn't really compare, but to an Audi TT, there is no contest, the mazda wins on the fun factor, insurance and overall the general great feeling you get driving one.
Once driven, you'll be smitten.
John