Do you own a home?
If you do, you could get a new car the way I'm planning on doing it:
Use the $20,000 to buy solar panels and use the money you save in electricity plus the $2000/year tax credit to make your new car payment.
Using my example, I'm installing a 2kW Solar Array that will save me about $80 a month on my electric bill. The $2000/year Federal tax credit works out to $166.67 dollars a month. Couple that with the fuel savings from driving a more fuel efficient car and you can save an extra $50/month.
When added up, it works out to be $296 / month - which will easily make a decent car payment.
The icing on the cake is the house will appreciate in value by about $17,000 and by having solar panels you won't need a generator in case of a power outage.
I'm doing a writeup about it on my site (work in progress):
http://solar.dashpc.com/