E46 M3 are great cars but there are a few things you should know. If you think a scoob is an expensive animal then the M3 will be an eye opener, they are a whole new ball game for everything with regards to expense. The engines are bullit proof, gearbox's great ( SMG are great when you get used to them) the rear diff's can be noisey and problematic at times, The fuel ecomomy is worse than a scoob, th epower is better than a scoob and no matter what anyone says will overtake a standard or lightly breathed upon STi at speeds above the speed limit,better fun ( rear wheel drive in the wet ) depreciate less and they eat tyres for a giggle.
Gimmie a shout if you need any other info