Trip,
PSS9 all the way. We (Terry and I) run it as well as some serious BSP guys. We tried the big $$$ Advance Design/GC system and it's too stiff even at full soft. Car just bounced around. It's amazing how well the Bilstein system works right outta the box. If you are nice, I'll even let you know what settings we're running
For a big car, the BMW handles pretty F'ing well.
Ed