Second vote for the impact. I made a tool at work to stop the pulley from spinning so I could get the bolt loose. I grabbed some extensions and a cheater bar and tried to break it loose. I pried so hard that the leverage I was using lifted the front end of the car off the ground!

I don't have the luxury of an air compressor and impact so I made a trip to a local garage to have them bust it loose. $10 and a two second blast with an impact had it off in a jiffy. I just had them tighten it up good enough to get back to my house.