OZ makes great wheels and is a supplier to many of the top racing teams. They have a solid pedigree. Unfortunately many of their wheels are produced in conservative sizes and offsets which don't interest too many M3 owners. Their 3 piece wheels are available in more aggressive sizes but they are somewhat heavy and the styles are dated IMO. I did consider their new racing wheel called the "challenge". It is available in 18x10 et25, black, no center caps. It's only available via phone order with tire rack because its a track fitment. They are around $400... The problem is they weigh 24lbs. Not horrible but there are lighter options.
OP - Thanks for postings picture of your SLIII's. I have always wanted to see how they looked on an M3. One of my favorite OZ wheels.
'13 M3 - Silverstone II - Sold
'04 M3 - Jet Black - BBS E88, KW Clubsports