Well... Back on topic..... what are your requirements other than 4 doors? What kind of power are you looking for and whats your budget?
An e36 M3 is pretty awesome, but like you say they are a little long in the tooth and will likely have some maint. needs, but that should be factored in when buying used, just a higher work order the older you go. Want more power? What about an e39 M5... those are pricey to keep going too, but pretty much rock solid 400 hp/4000lb beasts.
An NA e90... us 330i guys will tell you how awesome they are so I won't go on and on- cooling concerns? Really? Other than the elec water pump that will go when it feels like- heep a spare in the trunk- gotta do it, but thats the case with any elec water pump. Or a 335i with a stick and cooling upgrade (rad? Fan switch? Not familiar with the platform, sorry). Either case just looking at 1% more weight than an e36, but a stiffer structure to go along so you don't have to worry about subframe ripps or three wheel motion on sticky tires.
E90 M3..... Jesus H... best of all worlds. Unholy sound, gobs of power, utility for the 99.2% of the time when you aren't at a track school. Yeah, it's a pig on gas, but they seem to be pretty damn reliable. I'm hoping the new car puts the lci under 30k to replace my 330i (which will stay in the fam, I love that damn car). Simple mods just like the rest...pull the alignment pins to save the front tires from roasting, get rid of the front cats and a tune. Awesome car, truly the Goldy Lox, or whatever that broad's name is. The CTS V is a bitchin camaro/g6/gto yada yada with a motor that won't quit but at 4200 lbs it's kind of a pig. If it was 10% lighter I would buy a wagon with a stick in a heart beat over an e90 m3 for my next ride. They're awesome cars.
Anyone mention an e60 M5? The prices on those cars have TANKED. A guy a few blocks from me who plays for our hockey team (Meaning right now he plays charity golf :eyeroll
has an Interlagos Blue e60 M5. Sex on wheels. A bitch to keep up people say, but I feel like if it doesn't have nav and smg and other pricey/needless options it can keep the costs down. A pig on gas no matter what though.