It really depends on what division you plan to shoot in. Assuming Production with the S2, the fully cajunized would add substantial $, but should be noticeably better than stock. If you are shooting limited, you may want to consider converting to SAO, in which case it would be noticeably better than stock (assuming you don't mind starting cocked and locked) - This is also cheaper conversion/less parts than the full cajunized kit. I will say that what made the most difference in my limited gun was the hammer. With the stock hammer, when pulling the trigger, you could see the hammer cam back a bit before release - with the CGW race hammer camming it is almost non-existent.
If your new to CZ and adding parts etc. I'd lean to just having it done by them for more $$$ and be done with it. But, if you just want to change springs that is pretty easy and I wouldn't pay extra or wait for anyone to do that.