The fastest guys in my club in Seattle are running ARC or Awesomatix.
I picked up a used ARC R10 for super cheap a few months back and immediately picked up a couple laps compared my (albeit poorly setup) TA07, and shaved a full second off my lap times after a few weeks of getting used to the car and dialing it in to my driving style.
Everything I'm hearing about the Awesomatix is that you can build it box stock and go out and be super fast. There's really nothing that the car needs that it doesn't come equipped with.