In a previous lifetime I used to be in the printing racket, card stock makes all the difference from comparing out of work slackers printing shit out at Kinko's to the out of work slacker that can impress a downtown banker that you're really worth a hour of their time.
You only get one time to make a good impression, your card can do it over and over and over.
Look into some double-sided 10 point Kromekote, and pay a designer to work up your cards, get a real commerical print shop to print them and you will thank me in the long run.