944 turbo is about same weight and hp as a box s (250 hp, 2950 lbs) - you may just be trading into a car you already have. the Miata, while underpowered, is different in that it's only 2350 lbs. hard work to get a 944 or a 986 down to that weight. makes it a different driving experience. perhaps put your energy/$ into putting more power into the Miata:
Supercharger Kits, accessories, and electronics for MX5 Miata
or changing up the looks:
Jim's Blog