I had a similar dilemma a few years ago when I was seriously starting on the road toward FI, though in my case the sports car was an "extra" vehicle. The way I made my determination was to consider the cost for each thrill that the car brought me.
My calculation went something like this: For every year I owned the car, I was paying approximately $5000 extra between depreciation, insurance, registration, gas, etc. Meanwhile, I was probably getting about 5 days of thrills out of the car per year (annual autocross several hours away, occasional out-of-town trips, etc.). So I figured I was paying roughly $1000 per day of thrills. This was not worth it, so I sold it as quickly as I could, private party. Meanwhile, my motorcycle was also an extra, but was much more depreciated and got better gas mileage. I figure I spend roughly $500 extra per year to still own it, and that my per thrill cost is worth it to keep it.
I'm going to go against the grain here and not recommend a Leaf (or other pure electric car) unless it is not your sole car, if you like to travel at all. Other people say rent when you need to travel, but I think when you factor in rental car costs you've just offset any savings you've received by using electricity rather than gas.