Sounds like you want the rush of horsepower and speed mostly. The 135i with a JB4 tune would easily give you that for a fraction of the cost of getting a M. While a 40k miles M3 isn't worn out, the fact you might stretching yourself financially to be in it will only make you happy in the short-term. If money isn't a big deal, I say "ok" go for it (your young only once...etc.) but the smart thing to do would be stick it out with your 135i, add a tune, and maybe sell in 2 years. At that time, there will be a lot of '09 - '11 M3s with a lower price point that you can get into (if you're still interested).
Separately, you might want to consider a nice E46 M3 with lower miles for around $30k. It's really a fantastic car for the track, everyday, and modding. It's classic looks will last the test of time. Drop a supercharger in there for a couple grand and that car will fly.