Actually did this on Friday:

My 2004 Coupe never felt as tight as my 2005 Roadster - I'm the original owner of the Roadster and it's been running on a set of Eibach Pro-Kit springs and stock shocks for a few years now, but it only has 27,000 miles on it. Ride is firm but very controlled.

The Coupe I bought used last year with 75,000 on the clock and going over certain isolated bumps it always felt like the back end wanted to step out ever so slightly. It just felt sloppy compared to the Roadster, which is just odd.

Installed a set of Eibach Pro-Kit springs and new KYB monotube shocks on the Coupe and the slop is gone. Ride is firm, but waaaay better controlled than before. There is a specific bump on the drive to work that always felt really harsh when I'd hit it, and it's impossible to avoid - it's under the transponder bridge on the toll road and it crosses all lanes of traffic. I'm usually flowing with traffic when I encounter it, doing about 75mph. This morning all the car did was make a thump noise as the tires contacted the spot. No little jump or skitter, nothing unsettling in the least.

Huge improvement!!