And to truly post whore it, now I'll go so far as to actually post something somewhat relevant.
Before I fell in love with my Bridgestone Portenza SO3's, I went through a couple of less expensive, Z-rated performance tires. The first was the Yokohama AVS Intermediates. I'm not sure if they still make those anymore, it sounds like the ES-100's might be the modern day replacement. I liked the AVS' because they lasted for a long while compared to other Z-rated tires, and they were predicable when they let go.
Other than the Yoko's, I've also used Dunlop SP8000's. I think they were a little better than the Yoko's. They seemed to squeel a bit more at the limit, giving me a better sense of when they were going to let go. The Yoko's just kind of went, and recovered nicely. The Dunlops let you know what was coming.