I think you have to make a distinction between killer dampers, like Penskes valved for the C5, and coil overs. The Penske's are where most of the gain will come from.
Coil overs are only going to help if you really need to change your spring rates or your ride heights (the spring installed height change is usually necessary when you change springs).
What are you trying to gain? Is the car too stiff? Is it too soft? If you are not certain, then you probably aren't ready for them.
It is one thing to have a tunable/adjustable suspension and quite another to know how to tune and adjust it. To that end, I suggest Carroll Smith's series of books on race car preparation. And the bible of race car vehicle dynamics - Bill Milliken's _Race Car Vehicle Dynamics_. Fred Puhn's _How to Make your Car Handle_ is a fine starting point.
And even if you have that expertise, you need to have track time to do the testing necessary to understand the impact of the range of adjustment (springs, dampers, ride height) available.
Also.. I would not buy coil overs unless you have access to a good set of scales ($1500-$2000). Because getting the corner weights correct after adjustment is critical.
Don't forget extra tires for this testing and a race trailer to haul all this stuff
The suspensions on these cars are already so freakin' incredible that few folks can drive them consistently to the limit anyway. And at the end of the day, the fast guys who spend all their time driving their STOCK cars usually end up whooping on the guys who spend most of their time tweaking their modified cars.
Do you want to drive the car or adjust it? :lol: