Porsche Independent Servicing - JZM, 9e, RPM, Paragon

[c3m]

I'm looking for some advice on how to pick an indie to take care of my car. I'm looking for good customer service, high standard of worksmanship and attention to detail. I don't want my money to be going into maintaining shiny OPC showrooms.

I've got the following independents within reach: JZM, 9e (Nine Excellence), RPM Technik, Paragon.

How would you go about picking one of them?