I thought about this as well after loosing half of my 401k and IRAs. I am young so it wasn't a huge amount of money but it was more than I have ever spent on a car (which isn't saying that much).
Hindsight is 20/20 and I would have liked to have spent the money on something else but I also realize that cars cost money to maintain, insure and register. They also take space and it would still end up being just as big a gamble.
On that note I would read what Andy Reid writes in Classic and make a choice from there. He has been in the game for a while and knows whats going on. I think that E30 M3's will continue to appreciate but not at the rate that they have in the past 5 - 10 years. Think about the maintence costs as well. If the motor in a E30 M3 or 911 takes a crap on you it will probably cost you 5-15 years in appreciation. Also consider that a good paint job runs $5k+ and the repainted cars fetch less money than the original ones.
I recently bought a 47k mile Spark Yellow one owner 79 RX-7 for $2k. It needed some paint work and will undoubtedly cost me at least a grand in other random needs within the first year. When it is done it will fetch maybe $5k on todays market and I will have about $4k in it. If I keep it it should appreciate but the more I drive it the less its worth. I am now facing the possibility of being stuck with something that I can't drive much or modify for that matter. It is a fine example and something that I will really enjoy on a Sunday drive and can hopefully sell in 10 years and retire.(yeah right!)
Just some food for thought.
