There is actually a whole lot of valuable information discussed above, and I must commend all of you on a civic si vs. anything thread that was mostly based on experience and spec. I have driven the 8th gen si and driven the bloody hell out of a FR-S.
At heart I'm a mid engine lightweight fan when it comes to sports cars. I have also been racing an elise or mr2 spyder for a handful of years. When it comes to a street car, civic si vs frs is a tough choice. A good used si can be had for 13.5k, and is a very high quality automobile. Fun enough to drive, especially because you can't really have that much fun on most American highways any more. The 86, however is a platform that I can really make sweet love to. I just wish you could get one without all the traction control and tpms, etc bullsh. The requirements the automakers must meet for USA makes me sick to my stomach. Civic si or 86, both of them should weigh in at 2400 lbs if you delete all the crap you never needed. Still not sure which one I'd want more for a street car.
cheers!