you mentioned that you owe on your current ride, and that you have a fiance... M3, regardless of a vintage (from E30 to the latest ones) are not really family oriented cars and not budget oriented cars...

life sucks, as it has tendencies to make corrections to the plans - you already have a car that many will only dream about having... of course moving up is always nice but everytime you change a car, you take a financial hit (unless you go from a nice car to a beater) and with a fiance, i would suggest to keep the current car - you never know when she will get the "baby itch" and you will have additions in your cargo compartment...

on the other hand, you are young only once, and if not now - then when??? do what your heart tells you!!!