The best streetable options for track use today are the Bridgestone RE-71R and the Nitto NT01. Andrie Hartanto conducted a review and found them to be largely equivalent on the track:
Bridgestone
Both options should last you about 6 standard HPDE days, maybe more if you aren't pushing them. The NT01's aren't so streetable due to issues with heat cycling, so I don't recommend them if you only have one set of wheels. On the other hand, you can typically get a set of four 18" NT01s for ~$900 versus $1100-1200 for the RE-71R.