Tino, I'm running the old RM 4-pot setup on 328mm rotors. I don't know how the measurements differ between the 6-pot and earlier 4-pot, but for what it's worth, here are the wheel specs that I've run.
Work Meister S2R
17 x 8 +41
18 x 10 +45
No Spacers
Advan AVS Model 5
18 x 8 +45
19 x 10 +45
5mm Spacers
Prodrive GC-05F
17 x 7.5 +44
18 x 9.5 +44
5mm Spacers (but only for aesthetic reasons, if I recall correctly)
Advan RS
17 x 8 +37
18 x 10 +35
No Spacers