Please look at what is allowed in each class and decide what class would make sense for you. Based off you winning your class with a 100% stock car I assume you are in SCCA and D stock so I am writing this with the SCCA in mind.
In stock classes you can change wheels (if within 5 mm offset of stock and same size as original stock wheels), any tires including r comps, front sway bar, shocks, and break pads and fluid. So, if you want to stay stock I would do an alignment and shocks. Hold off on r-comps for at least season as it would be beneficial to learn to feel your car and your mistakes where r comps will hide errors. You can also dd street tires. Most of the national winners on street tires were on Dunlop Star Specs. Nationally integras have owned this class for a while.
For Street Turing Ultimate you can only have street tires but for the most part any suspension mod as long as you don't change mounting points or replace rubber parts with metal ones. All exhaust mods as long as you have one cat I think. Intakes and tunes that don't change boost are okay. I am pretty sure you can do roll cages, harneses and racing seats. I race in STU and am competitive locally with my mods but not nationally. I have very nice coilovers, the front m3 bits, camber plates, and lightweight wheels with as much rubber as I can fit without rubbing.
I would advise against kw unless you go up to KW Clubsports and for that much you have better options in my opinion. The KW 1, 2, and 3 all have progressive springs which are made more for the street than the track. While square tires is an easy way to give you a more neutral balance they will decrease grip. You are probably better off dialing out understeer in other ways and getting a bigger rear wheels. I don't wear through my tires unevenly side to side so it does not save money to rotate other then the smaller tires being cheaper. If you don't have camber plates plan or chewing through front tires at an alarming rate as they will roll over the edges and you may get camber sheer.
I may not win nationally but I am building my car how I want it. I suggest you do the same. In that case I recommend decent tires, shocks or coilovers if you can afford them, camber plates, and as much seat time as you can get. If you want it to be easy to rotate the back of the car then maybe a square set up makes sense for you, just be aware you are not getting 1000 points with it. Make sure to focus on what you want and not nessisarily what will cut the time because you are going to enjoy your car not to win a key chain.
2011 BMW 135i DCT M Sport, black sapphire metallic,Coral red tint, Apex ARC8, 235/265 Dunlop ZIIs, Ohlins coilovers w/ Swift springs, M3 front bits, Whiteline rear sub frame bushings, Vorshlag camber plates, Stoptech pads, custom exhaust, stud conversion, spacers
Last edited by Clovef; 09-13-2012 at 11:26 PM.
Reason: I am a dumb jerk so I often need some editing. Sorry