By far my cheapest option is just keep the car I've got -- a 2009 Matrix with only 100k km on it.
I was just thinking about trading it in now because I can still get a good trade in amount for it; not much less than what I paid, not much lower than what private sellers are asking, and saves me a lot on taxes too.
I'd get something off-lease or a few years old for around $15k and be done with it.. but that's just my general outlook on daily drivers. I'm sure if I was rich I wouldn't care about the soundness of a vehicle 'investment' but the numbers just don't work on a new car, IMO. I can't imagine how people feel when they're 4 years into a 60 month loan, still making the same 'new car' payments on their now-used car.