Yeah I can highly recommend the Cossie / AP kit. One of the best mods that I did to my car. They give so much more confidence on track and will take whatever you throw at them in their stride whilst staying consistent throughout.
If you don't want 18's though I'd recommend the standard AP kits or one of the Reyland kits that are AP but with their own mounting hardware or disc options that can reduce the cost. There are also other kits out there that are just as good but I'd stick to the proven brands such as AP, Stoptech, Brembo and Alcon (Megabucks, but pretty much cream of the crop in terms of brakes)
It's really not worth going for the cheaper kits like K-Sport if you're serious about tracking. Proper kits are built to handle much more stress and are also lighter and give better feel which is important when you are braking as late as possible on track, you need that confidence that every time you hit that pedal you are going to get the braking performance and feedback you expect and that they will never let you down.
Also don't get caught up in the "more pistons, means it's better" BS, this isn't true at all and is normally how most of the cheaper kits try and blag that they are better. A well designed caliper with fewer pistons can easily outperform a badly designed one which just has as many pistons as they could cram in there cause bigger numbers look better. I've toured Alcon's factory and the amount of engineering, R&D and product testing that goes in to making these kits is insane, you won't get anywhere near that with cheap brands like K-Sport.
Definitely get a master cylinder brace too as others have suggested, improves the pedal feel quite a bit, especially under heavy braking.