Do you need the rapid spring changes of coil overs or the additional engine room provided by a new frame? Are there rule sets to be concerned with regarding the application? Nearly any coil over conversion is going to be many thousands of dollars. Stock based stuff is going to be more price friendly.
For stock based components, Hotchkis, Firm Feel, and QA1 make a very nice packages of parts that all work together and can be upgraded individually to save the all at once budget hit. These components can be put together in sucha way to create a handling package capability beyond most driver's ability to tune them. Nearly any of these can used to upgrade an entire car for around $3k, give or take a few hundred.
If you want complete coil over suspensions, the Alterkation makes a nice package using M2 spindles. XV Engineering also has a kit based on Vette parts. There are a couple others similar to either of these such as Control Freaks and Magnumforce, although on of the Magnumforce kits has the same shock tower support issue as the Bob's unit. Most coil over kits start at $4k per end and go up from there.
