I have the smaller Q45 brakes and have been on the same Hawk pads for over a year with out issue. I've yet to see a reason go bigger. Some SCCA classes usually run stock calipers. They just use really agressive pads, good brake fluid and lots of ducting to keep everything cool.

I dont know if my brakes will hold up to multiple 140mph stops though, and I dont plan on finding out.

SPL style brake ducts help out alot too. Simple to make and they work.