Keep in mind that bolt ons for the S don't gain much power at all, and many available bolt ons are even losing power.
You will have to have an exhaust made for the swap, and it's likely you will lose power there as well.
I'm a huge s2000 fan, but the reality is there is no extra power without going the turbo or SC route.
Just be ready to explain why you lost to a bolt on L motor for 4x the price.
I hope you do the swap, and don't let the negative comments get you down. Good luck with whatever you choose.