i used a few sets of ecsta supras 712's. they're...well....different. For the price, you can't beat em. They worked fine for me, but don't expect them to last too long. I had 3 auto-x's, with practice days, a trip to N.C., 2 runs up the dragon and back down, and then the following weekend returning back from N.C. the tread separated from the sidewall. All in all, they're cool for auto-x, especially if you're still in g-stock.
however, i did get a set of dayton zr-16's...which were pricey, but when they warmed up they were grippy as fricking hell. Drive while the road is colder, or wet and you get nothing, but for dry they're just badass. However they were around $550 for a set of z-rated 16's.