The 5 best used sports cars that sell for under $20,000, according to data

Ly calls the Mustang a "classic American sports car."

"The 2012 S4 has a supercharged engine and has the superior ride and handling characteristic of the Audi brand," Ly said.

Ly claims the Charger — a "consummate American muscle car" — appeals to consumers who want a spacious and powerful car.

The used 2014 Ford Mustang convertible is, on average, less expensive than the used non-convertible version.