Advice for processor for media pc

[Paradax]

Alright im building a media oriented computer (audio and video editing software and multimedia presentations) and im trying to decide between a phenom ii x3 720 or a phenom ii x2 550. I'll probably try to unlock the extra cores one either processor. Does anyone know if either one of these has a better record of being unable to unlock the extra cores or is it just luck of the draw? Also im assuming the extra core would probably outweigh the higher clock speed for av editing?

 

Thanks for any suggestions.