Is the ride kinda bouncy now? How many miles on the stock struts?
B/c if the ride is bouncy your stock struts maybe on their way out. The stock struts tend to start failing at about 80K miles or so and lowering springs only accelerates that due to the lower stance and higher spring rates.
Edit: Just noticed you said it rides over bumps solid. So you could be right your original bump stops maybe worn out. You should also check your CV joints/boots as they can make some similar noises when they get old/rupture. Also, its possible your sways bushings may need some grease.
I believe RCE still sells prodrive springs, so you should contact them and see if they can get some bump stops for you:
Welcome to Racecomp Engineering.com