You make some very good points. Also, SLK320 vs an AMG ;-) no question about what I would be forced to do from a cost perspective. I'm also sure that an extra 100hp under the hood would make for an extremely fine ride. To be honest, I would consider putting a low boost kit on my XFire but I would have to be pretty sure of its quality. Not only fit and finish but even more important to me is the drivability which includes fuel and timing management. A car that dies when coming to a stop, has cold start problems and knock (just to name a few) = NO FUN. I guess using the SLK320 guys as a source of info is by far the best option. If many of them swear by the kit then its likely to be a good solution.

The final issue for me is installation. I have installed a supercharger and a turbo on Miata's and it was not extremely difficult. I would much rather do the install myself and save that added cost if possible. Not sure if any 320 owners have done their won install or not. Might be worth asking.