I had my "show" 20" FE wheels diamond cut a few years back by Pristine in Milton Keynes, with the aim of getting them a close as possible to the OEM finish: that's not actually possible, given the way Audi shotblasted the side face of the spokes, but I was still very pleased with the finish (very few people would notice they're not OEM)
The complication with diamond cutting is that the finish is then more susceptible to surface damage than a regular "smooth" powder coat/clearcoat combination. To combat that issue, I then had a coating of MetalMate (
http://www.metalmate.info/www.metalm...o/WELCOME.html) applied. This gets mixed reviews, but seems to have done the job pretty well.