Read TRire Rack's review of the Sumitomo ZIII. Hands down the best tire for the money.
Good tire for the money but no where near the dry grip as some of the other tires mentioned.
Sumitomo ZIII = 0.92g
Dunlop Direzza Sport Z1 Star Spec = 0.97g
Michelin Pilot Sport PS2 = 0.98g
Bridgestone Potenza RE-11 = 0.99g
Kumho Ecsta XS = 1.01g
Michelin Pilot Super Sport = 1.07g
There's definately varied opinions on this, but I don't care about the "N".
I just had a set of Pilot Super Sport tires installed, and they're fantastic, even compared to the PS2's they replaced. A good deal more grip, even below 50 degrees.