Hi Bill,
1. I've been using Sumitomo HTR Z III's on my 2005 Boxster, and I've
been very happy with them, especially for the price. They've done well
for me at the track, on the autocross courses, and of course driving on
the street. At one point I bought a set of wheels that had some
Continentals with some life left in them--I believe they were
ContiSportContacts--and those seemed reasonable as well, although I
replaced them with my familiar Sumis when they were used up. Of course
there are a bunch of other tires that fit these cars, and everyone seems
to have their favorites...
2. The last 55K miles on my Boxster have been driven with non-N-rated
tires, and I have yet to observe any ill effects. (Others who have
observed my driving may disagree ;-)
3. I'm pretty new around here, so I don't have any firsthand experience.
However, back in Colorado, there was a tire shop that sold the Sumis at
a price comparable to the Tire Rack's--so I'll bet there are local deals
to be had as well. Hillside Tire and Bob Jones Tire are both owned
and/or operated by PCA members, and Foothill Tire Pros has sponsored a
few of our events, so these might be good places to start.
Enjoy your Boxster!
Cheers,
Jeremy
--
Jeremy L. Rosenberger *
jl...@cornell.edu
http://www.slaq.org/jeremy/