You are supposed to be able to run the 13lb spring with the standard firing pin but I personally won't run anything less than 15lb on the hammer spring as I consider all my CZ's to be defensive pistols. If you are moving toward the complete pro package it's best to either buy it now or wait till you can afford it. Piecing the gun together in stages may cause more issues than you want especially if your not used to dealing with the CZ action.
I have no experience with the Carbo spring kits, others here do and seem to like them. I generally add the CGW Pro Package kits to my CZ's so buying springs elsewhere makes no sense. I've gotten all 5 of my current CZ's to have the same trigger feel doing it this way. I do keep extra springs on hand for my CZ's but for what it's worth I've never had a sear spring failure in any of them and 2 of them have north of 25,000 on the originals.