Oh yeah and I have the UUC SSK.
I went for the AA Tuning clutch and LTW Flywheels because I wanted something well known that I knew could handle the power. I am int he process of doing major power upgrades and really couldnt for for a standard clutch. I also went with the UUC SSK because it came with other parts that normally dont come with other brand SSK's which usually make those cheaper, but you end up paying for them later when they wear out.
UUC SSK is the way to go. As far as a e39 goes, Id ont know if AA Tuning makes a good clutch for you.
By the way, the clutch disc and 12 lb flywheel cost about $1500, not including install.