First of all, lets talk about your size selection. 255 is an oddball size, and does not sell a lot of tires. This affects pricing, as you will see that that extra 10mm in tire width will cost you 20 dollars extra per tire. Might as well pay 10 dollars more and run a 275. You are not going to get any difference that you will see on the street. More over, wider tire will increase roll resistance, add weight and cost you in gas milage.
Secondly on the tires themselves. The only good nitto is a R comp nitto. 555 gets greasy as hell under track conditions, and I know this first hand. If you are looking for some really good rubber that will perform on the street or the track, I'd highly recommend Kumho Ecsta MX. It's not much more than 555, and is a much better tire in every respect. It does not overheat at the track, has stiff sidewalls for predictable and crisp handling. Another tire I'd recommend personally is Avon Tech M500. Dirt fucking cheap (because they are closing them out at TireRack), and these perform AWESOME at the track. A little slippery when cold, but they can stand up to a 35 minute hot lap session on fast track without ever overheating. The only complaint I had with them is that the sidewall is a bit soft, but that could be compensated by running a little more tire pressure than usual (went from running 32psi on all 4 to running 35psi on front tires for better steering responce).
