I myself am fairly new to Autocross, I've only run with FAST so far and I couldn't be happier. You guys are awesome and I can tell you have a passion and understanding of the sport.
I'm currently driving a 2015 Ford Focus ST Boosted w/ stock Goodyear Eagle F1 asymmetric 2's on 18's. The tires are pretty much on their last leg especially for Autocross purposes!
I really don't daily driver my car, I have a separate work vehicle so my car sits at home mostly. 6500miles since July 2015...
I plan on auto crossing at least one a month or every other month if the wife is on my case.
If you were in my shoes would you try the Federals or Nexen's?

RS-R 235/40/18 - $127/ea free shipping (eBay)

RS-RR 245/40/18 - $127.50/ea free shipping (eBay)

Nexen SUR4 - 235/40/18 - $139/ea PLUS $60 shipping (TireRack)
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