I purchased my Stage 4 kit from UMI. I spent a good half hour on the phone with them, talked cars, info on the green machine, bounced ideas off them and got really good advice for my build. They threw in a few extras, worked me a sweet deal on shipping to Canada and gave me an invitation to come race any time I'm "in the neighborhood".
That side alone was pretty much a win in my books, but the quality of the products are top notch to boot. Fit was great and the finish of the parts is beautiful.
I haven't done business with BMR yet but I can say my experience with UMI was pretty much perfect. My $0.02.