Keep in mind the maintenance on an M car is amplified quite a bit. Performance everything parts that have shorter life cycles to replace. Tires go fast, brakes are very pricey, spark plugs every 10k to 15k, etc. The mechanic labor rate is amped up for an M too.

I got a used M2 comp that was still under manufacturer warranty for a little less than a year. Enjoyed it for 6 months and moved on. Whelped a lot of money, glad I scratched that itch, but honestly it wasn't worth it.

All that to say, the way I did it is a more practical approach than buying new.

Will also say you'll find a 340i isn't that much of a compromise vs. the M3.

I've owned a 135i, 128i, and M2 comp. In reflection my favorite was the 128i, it was still quite fast and great handling but it was simple more agreeable in traffic. The M2 only wants to go fast and isn't fun inching along, granted being a manual didn't help that.