Tough choice - my brother is selling his E46 M3 and will be getting a 5-series Bimmer (F10). The M3 is almost 10 years old (E46) but still in very good condition and has low mileage. Looks great too. I test drove it a while ago and its power is definitely much better than my current SLK 350 convertible (2002). The only downside side of the M3 is that it's not convertible - and maybe the SLK has better style.
Chings, if you can choose, would you keep the SLK 350 or get the E46 M3?
Correction: M3 is 2002 and SLK is 2005. Please ignore the year in the voting options.