The off putting thing about an E46 M3, for me, is how dated they feel inside. However the upside is how well and rewarding they drive, and how frugal they are in normal driving.
We looked at supercharging a customers car, and spoke in depth to CA automotive, even got to the stage of demoing their outrageous 500plus bhp yellow car!- check it on their website. Anyway the point I'm getting to, is it not just a case of slapping a charger on. Brakes need to he uprated, as they're sh*te, uprated clutch, new x pipe etc, and all this fitted with the SC kit was north of ten grand!! And what a lot of people forget is the general running costs as pointed out above.
However, I do agree, they are an itch to be scratched, and well worth it, if you get a good one. I'm lucky enough to have driven and sold lots, so my itch has been scatched, I just have the 911 one to sort out, but the plans are in place for that one.......