Coil overs are great for racing, when you NEED the fine adjustability to gain that extra 1/10th a second in your lap time, Much like like 14" 6 piston brakes, its nice to have but its an overkill for the street.
The most important part of your Suspension is the Springs and they work directly with the Shocks/Struts, these need to be changed together, or else youll get the lok and not the performance.
Sway bars help the car stay flat when turning hard but they are depending on the spring/shocks combo to do their job, if you plan on runnnig your car hard, i would also suggest you get better mounting hardware for your sway bars, billet is generally strongest and most light weight.
Upper control arms and the UCA mount will help your car put the power to the ground better, especially in a drag race situation.
Panhard bard and panhard brace reinforce the rear end suspension, 80% of S197's require them because one wheel will stick out farther than the other when you lower the car, the adjustability will compensate for it.
Tie Rods (Bumpsteer Kit) and Ball joints will help correct the suspension geometry that was upset by lowering the car, although these are not a MUST, they will make your car track straight and not veer off when you hit bumps. Camber plates will allow you to fine tune the negative camber on your front wheels, more negative camber gives you better bit when turning as you wheel will be angled IN on the front but it will chew through your tires much faster and unevenly, the trick is to find the happy medium for your driving style.
Suspension components work in harmony, if you change one thing you disrupt another, so its best to do everything in one shot and then get an alignment. Like Arkady said, it will cost about $2 Grand in parts but you will be able to hang with the Euro guys when it comes to turns. Wider and lower profile tires will make a huige difference as they are the only part of the car that actually touches the ground.
Hope that helps but you got a lot of research to do.
