[recycledsixtie]

You could consider doing a matrix like this.

For instance what might be say 5 important factors in choosing a car?

These might be mine. You could consider what do you value most.

On these value factors attribute numbers from 1 to 10. Ten being the highest value.

For me five factors would be and attribution of values to them are as follows:
1. New 5
2. Reliability 10
3. Driveability - steering, brakes, suspension 10
4. Discounted price due older 10
5. Options that I want 9
Total score 44 out of 50

Now set up a matrix like this with some value factors that you value and attribute scores to them. It can help you make a decision.....other factors might be P warranty, engine, S or base etc etc....
You could put a matrix next to it of say a 4 year old Boxster and see how it rates next to new. Hope this helps!