All those mods you want to do will decrease slop, increase the directness of the steering, and in general, make things seem even more twitchy to you.

What was the last car you drove that makes you find the S2000 too responsive?

 

go back to the dealer you took it to, let them know you are not happy with the alignment they did and ask for the UK/European spec alignment. If you do a search on here, you will find what those settings are. I did this just a few months after I bought my car new and it made a very noticeable difference for the better.

 

Danteediss,
Did you make any changes to fix the problem? I am having the same issue with my 2004. I had it aligned according to US factory specs, and I have new tires (factory size, I believe they are Goodyears). I don't believe my problem is within the alignment, or tires. My car is twitchy and unstable at high speeds, it almost feels like the sway bar is not working property. Keep me posted on what you try, and I'll do the same. Thnaks.