Balo makes a very high quality rotor. They also don't farm out the casting of the rotor. It is done in-house in their foundry.
For the heavier BMWs this brand stood out as having an excellent reputation for not warping...and it was one of the least expensive.
'85 380 SL (sold)
'85 Carrera Flatnose
'71 280 SL Signal Red/Cognac