The miata's can put down great numbers in relation to their weight very easily and MUCH cheaper than the v-8 swaps(most v8 swaps end up costing in the ballpark of 12-20 grand, where a turbo setup would cost 2-6 thousand for the same HP). Lots of boosted miatas around. Jackson racing uses a small M45 charger, but it is much better to go with the MP62 if you feel you will be bit by the power bug!
I had turboed mine with a gt2554(yes a small VERY responsive turbo) injectors, intercooler, stand alone engine management, etc, and was in the ballpark of $2200 with about 220whp at 14psi where a stock 95 puts about 100ish whp. The car was pretty damn fast and felt even faster!
Internals of the engine can easily take 250whp but the 5-speed tranny starts giving out around those numbers(can be remedied with the 6-speed).