Hey, Z,
Powder coat is definitely the way to go, especially when you are building a car of the caliber of your M-spec. My last three cars received PC; no regrets. The mach build is also a smart move. I'm a huge fan of mach builds and believe it's the best way to build a car. While it's not a se7en, I've posted a few pics below of a '26 track T that I built a few years ago. The build process was mach build, blow apart, powder coat, paint and then put it back together like a Monogram kit. You should start a thread in Member's Rides and keep everyone updated on your build. Also, do you have a Stalker V6 Gallery build site started?
With the M-spec being relatively new to the family of se7en-style cars, I see lots of questions pertaining to M-spec builds floating around on the Yahoo Groups forum. I think several of those folks with questions frequent this site as well for information. Any info current builders can provide about the build experience/process of the M-spec can be invaluable to others as well as to new builders down the road.