If you're thinking about signing up as a driver for a ride-sharing service such as Uber or Lyft, you'll want to make sure that your car of choice is up for the job. How many seats does it have? How many doors? What type of amenities? Is it comfortable? Just in case your current car won't pass muster, we've listed seven excellent new choices for drivers interested in upgrading their ride to offer the best possible experience for their passengers.