FSDs will work fine with those springs, and they will make a huge difference. I recommend riding in a car that has FSDs to make sure you like them. They are very different from anything else. The ride is very soft over bumps, but they firm up in turns and manage to do both in bumpy turns, which is my favorite thing about them. I have them in my car and love them for street. There are better options for track but with nowhere near the ride comfort. Here's a graphic from a Koni ad that I like posting to annoy the Koni Sport guys:
