Yeah, except for the BB. The 6600 is the new integrated spindle type with outboard bearings. I'd say if you don't know the difference,buy the 65oo and have lots left over for beer.
I may be a bit thick. Based upon your response - The 6500 cranks will work with the 6600 bottom bracket as well as all 6600 derailleurs. I love beer so the savings is significant. Is there a performance advantage with the 6600 cranks?