With the mods currently avilable for this beauty, what can be acheived (HP, torque, top-end) by this car without having to rebuild it every 5k miles?

 

If you're looking for 9-seconds quarter mile S2000s, I don't believe any one of us know about it. Import Tuner magazine featured an S2000 with turbo on it, but that requires a lot of work and $, plus you'll usually end up having to lower the compression ratio.

Moderate gains with headers (~$1300), lightweight exhaust (~$600 to ~$1500), throttle body bore (~$150), FPR (fuel pressure regulator (~$150) or Apexi VAFC (~$400), better air filter (~$60 to $1000 - don't remember how much Mugen's CAI costs) can do pretty well on the S. Just don't expect magic.

Comptech has a supercharger out ($5K+) that's supposed to pump some extra ponies, but none of us know what the long term impact that has on our engines.

If you are looking for a car that's got huge aftermarket options, look for an Integra or Civic.

But of course I believe the S2000 has the most owners designed, professionally made accessories from leather goods to body kits.