i'm on the 205/50/15's right now, and unless you're willing to shell out for $150 BFG/S-03 in a 225/50/15 trim, there's no other tire to be on for auto-x.
although i really wish falken made a 225/50/15 azenis. need more rubber under my car to compete with all of those damn 2600 lb ITR's or AWD WRX's...