What is this AMD promo code that you speak of?
You can get the info here: http://www.cheapassgamer.com/forums/showthread.php?t=299782
I believe it is actually dead ( as they ran out of keys.)
Yes ! , it clearly says :
We're sorry, but the DiRT®3TM promotion has ended and we're all out of codes! You can still take the quiz to vote for your favorite Challenger!
Don't worry , it will probably get on offer at Steam some time in the future - also remember to check their daily deals - where you got your "Vampire: The Masquerade - Bloodlines" ;-)
I don't hink that I have bought anything from Steam at full price yet......