I bought the Sumitomos that you list, and they are very good, but I do not autocross, and I suspect that they would be not so good at that.
You do want to pay attention to the UTQG number.....which roughly describes the hardness of the compound. A low number (300) is softer and a high number (600) is harder and usually found on tires with a wear guarantee. There are very few (maybe none!) 15" tires left with a low UTQG number(summer only)....and they are pricey. That is why I ended up with the Sumitomos.
edit: The T/As have a reputation of getting harder as they age, so you may see an improvement with the Sumitomos or the Firestones.
[This message has been edited by Gall757 (edited 11-13-2014).]