Just checked my records and the service we have used the last time we were in New York is from

http://www.dial7.com/

Picked us up at the airport no problems and was waiting in reception at the agreed time ready to take us to the airport.

A town car (bigger than a normal sedan) is $53 to either airport, however you need to add any tolls (bridges/tunnels) to this, plus a tip for the driver.

Regards Dave