I'm not recommending any tire, but I will say that my experience with
using Continental ContiExtremeContact on two  C5's was great. They
were non runflats and priced right, $132 front, & $175 rear, plus the
cost of an air pump and repair kit like GM puts in the C5 Z06. One
thing to consider is that most repair facilities can change these tire
but can't touch the stiff sidewall of the Goodyear runflat. The
Continentals are sometimes used as OE on Mercedes-Benz, Audi, Porsche,
and BMW. The Continental's ride, wear, and noise were all better than
the Goodyear runflats, better adhesion in rain was only slight. The
softer sidewall needed a bit more air  pressure to keep a flat patch
on the road. Had to get it from a BMW tire sticker, everyone is lawyer
shy and won't tell you to run anything other than what is on your
door, neither will I.

If they made a 19" tire I would have a set on my C6 today.

One last note, if you check the UQTG rating you will see that it
exceeds the OE tire by Goodyear although the speed rating is W (168)
versus Goodyear's Y (186). They are also 6 and 10 pounds lighter due
to the more common side walls.