I don't have the CS-2 but I'll be getting one. I've been researching for a little over a month and can't see any better option than CS-2. A few things to remember...
1. The up-pipe manufacturer isn't critical, just get one.
2. The down-pipe manufacturer isn't critical, but don't get a Flat-Plane (like HKS).
3. You can go CS-1 with no other mods, an excellent first mod.
4. You'll need a down-pipe to go CS-2.
5. If you keep a single cat your car will be quieter, less smelly, and blow less black smoke while losing only a few HP. My suggestion is that if this is your intent, get a high-flow model.