Personally I would say the Nitto 450's were some of the least gripping tires I've owned and IMO were only a small improvement over the stockers. I could set the 450's free pretty easily, making 1st to 2nd spinning no prob, and this was on the t-25. They lasted less than 12k miles, which is horrible for a tire of its wear rating (30k + miles), and most likely because they just spin too easy.
The 555's on the other hand are fairly cheap for their performance, tread life and speed rating. Now with a bigger turbo and wheels, they will not let me light up shifting from 1st -2nd (unless of course I purposely dump it). I do lose traction at the top of 2nd WOT, but that is expected from a 320+ whp FWD and there probably isn't a tire out there that will hold it. I have nearly 25k miles on these, with still about 20-30% to go. They have a much less wear raiting than the 450's and I've doubled the life compared to the 450's (I too am Surprised as I never had a tire last so long). I paid close to $225 ea for the 555's, but then again I'm at 19", which is a major downside for cost (and performance). 17" and lower are in the $100-$150 range.
I'm pretty sure the Nitto 555's are some of the cheapest high performance tires there are, and you will get way more than you pay for.
I have a friend with the khumo (720 or something like that) tires on his LX mustang. Avoid these. He now feels like he has a GT because he can spin his tires shifting from 1st-2nd, and its funny how he tells me stories about how he smokes GT's on the freeway (he is completely stock V6 btw and slower than a snail).
Another tire I have experience with are Pirelli P-Zero's. Not worth the $200 premium you pay for the name, although they definately are good tires, but not much better than 555's. They lasted a whopping 9k miles. I'd be happier flushing the extra 600-800 bones down the drain then buy these again knowing that 4 months later they are toast.
I've heard continental makes some good tires for the price but I've never owned a set.
Good luck. Tire selection can make you or break you and in most cases, you get what you pay for.
[Edited by Cazzo on 11-30-2001 at 01:34 AM]