I just picked up a set of the RS3s in 195/15, and also have some 225's. While I do like the Rivals and consider them a superior autox tire for SCCA competition, I would take the RS3 if I had to select a single tire to do all my driving on. No other tire can truly handle Texas heat, track, autox, street driving and significant mileage like the Kook. The closest thing to them is the old Star Spec, which never took heat quite as well.
Having said that, I am planning to compete on Yokohamas this season. :D