If you get a rotor like the DBA 5000's which are a 2 piece with alloy hat, then you will only have to get machine work done once. Yes they cost alot more, for the first purchase, but then the rotor itself with no hat is simular price to the 4000's anyway.
Thats what im doing.
Plus on a personal rant and my 2c, i wouldnt rate wilwood as a 'race car' caliper, and as said above not ideal for the street, so ??? They are cheap tho.....