As has been asked a couple times, .... what do you want out of your car? What are you going to "use" these brakes for?
As many have said, the Z brakes (or similar) will sufice for daily driving, lite autoX needs, etc. But obviously you're not looking for something like that.
The main thing to mention that is of concern when upgrading your brakes is brake fade! I mean Z brakes are nice, but damn they fade fast a s*** on a track!! So if you're going to be doing an occational track day and don't want to deal with that, a 2 piece rotor is the way to go.Best bang for your buck IMO are StopTech kits!

http://www.stoptech.comWe've used them on track days beating the hell out of the brakes and they hold up great! A 'little' fade, then they hold over and over again.
Rotora's seem ok, but I've never seen them in action. Willwoods have had some problems with noise, and unreliablitiy in my experiences.
just my 2¢Sean