Well, desired application really should drive what you do to your suspension.

For the occasional bracket racer and regular street driver, the stock stuff can be dialed in to work very well while increasing handling capability and producing more consistent strip times, with only changes to spring rates and shocks. This can be done from under a grand to several thousand dollars depending on if you want to piece meal it or buy a complete integrated update to the OEM layout.

On the other hand, if you are racing in a series that allows the modifications, you want the weight reduction, you run a variety of tracks regularly, need the range of adjustability, and will be changing springs and shocks based on the track or conditions in a circumstance where tenths or hundredths of a second matter, then a coil over conversion may be the best ticket. Prices here start at several thousands and only go up from there. The top tier pro-touring type guys can easily top out $25-30k for a suspension system.