Buying bulbs at Wal-Mart isn't a bad idea, because when a bulb burns out you can put them back in the package and exchange them for a new set. If you really got the nerve, you can buy some silverstars, install them, and put your stock bulbs in the Silverstar package and get your money back.
I've noticed people have done that at my local Wal-Mart.
Anywho, the Silverstars are nice bulbs, I recommend you get those.