Ok I will throw in what I know from my single seater racing experance. First off a bone jarring ride not only pounds your kidneys but it also kills the cornering speed on your car. I can't tell you how many student cars I get into at track days and almost immediately ask" do you have the shocks full stiff" A really stiff set-up will make the car very skatey - it will feel fast because it gives instant feedback but it will slide a lot earlier than a softer set-up. If the wheels are not be able to follow undulations in the road then the tires aren't on the ground so they are not building any grip. Further when you watch Indy car races or F1 and it rains the team soften the car up to build mechanical grip. A friend of mine is the leading Triumph GT 6 racer in the country and Kas Kastner who raced for Triumph is always telling him to run the car slightly softer than what feels racey. Same as if your car is so soft it bottoms if you car is to stiff it will efffectively bottom out when the wheel makes a sudden movement , so that wheel as no grip. For the sake of argument if you have four 7 inch wide tires you have 28 inches of tire on the ground , if one does nothing for a split second you have 21 inches of tire on the ground. If this occurs two or three times in a corner then obviuosly the car will go slower. If you have ever driven an unloaded full size pick up down a wash board gravel road you know what overly stiff suspension does.This is no different then setting your car up to oversteer. Oversteer is fun but it's slower than a car with a hint of understeer.(Alain Prost's words not mine)
Now with all that said buy good quality shocks , springs and a matched set of sway bars. You need to match all the suspension components to each other to get the most out of them. You can use parts form the wreckers as long as the work together. The C-sedan set up that is on this pages works very well and it is essentially what I use. 7/8 front bar , 1/2 rear with Tokico strut inserts and a set of old non-gas Koni adjustables. (The Koni shocks work well for fine tuning and Koni will still service them). I cannot remember the spring rates but the springs are straight out of the NISMO catolog. So remember bone jarring is just as bad as the car bottoming.

My $0.02 Tom Grossmann