To get Collectors Edition cars, you have to complete the indicated task in the Challenge Series:
Aston Martin DB9 (Exotic): defeat Wolf in Boss Battle mode
Dodge Charger RT Classic (Muscle): defeat the 21st Muscle Car Gang
Jaguar XK 2007 (Exotic): complete all three Turf War races
Mazda RX7 (Tuner): defeat Kenji in Boss Battle mode
Nissan 240SX (Tuner): complete all three Checkpoint challenges
To unlock Crew members, you have to complete the indicated task:
Sal: 4-6 races
Yumi: defeat Kenji/Bushido
Colin: defeat Wolf/TFK
Samson: defeat Angie/21st Street
Nikki: defeat all 3 beginning Bosses