Spacers aren't needed with genuine CSLs or reps (.5" wider than ZCPs).
I got my reps through **********s.com, killer price and service.
Link (select M3 fitment):
http://www.**********s.com/_e/Veloci...d_M3_cars_.htm
They weigh 24lbs each, which isn't the lightest on the market but they're strong enough for harsh track duty and so cheap that they're almost expendable if you do bend one.
For $750 a set of good looking, strong, perfectly-fitting wheels, I'm certainly not complaining. Remember, when it comes to wheels, pick
two of the following: light, strong, cheap.