buy a set of sticky tires. simple as that. why do you want to stiffen up your steering and tighten up your turns? those mods don't make your car grip the road better. you don't want a roll cage, unless you want to bash your head in if you get into a small traffic accident.

to sum it up, get a set of better tires, i'll start off by listing some good ones:
kumho mx, falken azenis rt615, hankook rsz212s.
edit: bushings are a good idea, but they're pain in the ass to install.