I cant remember now off the top of my head, but didnt SP1 come out prior to extension 1 and 2?
Ex 1 was the muscle plug in but Ex2 was a full install which I think had the updates to SP1 included, then again you need to be a gold member to have access to Ex1 and 2 so it might not make a difference.
"No pressure, no diamonds" Thomas Carlyle