As others have mentioned you should buy new over that used M3. I saw your comment about a discount, but even with that you’re still probably better off just buying new since I can’t imagine they would come down too much on their asking price.

If your concern is the ease of trading in, explore other options for selling your current vehicle. Get a quote from Tesla and carmax at a minimum. Also, see if the dealer with buy the car outright rather than a trade.

I got quotes from 6 or 7 different services for my 1-year old 4Runner. There was an $8,500 gap between the lowest and highest offer. Most offers were about $2,500 less than the top offer. The quote from my local Toyota dealer was the worst, and they were real cocky bastards about it too.