of course powercleans
increase muscle mass, any olyimpic lifter over 200lbs is pretty big and built, most of them if it were the 40's-60's could step on a bodybuilding stage.
of course though if you wanted to get huge you couldn't do that powercleaning only 200lbs (200lbs will put mass on though), look at guys like Ken Patera, I've seen pics of him and he didn't get that way doing only squats, he powcleaned over 400lbs squat cleaned 500lbs, most ol. lifters don't even deadlift, some of the old-school guys didn't squat much eithier, they just did the lifts (SOME, NOT ALL).
I bet ya the bigger your powerclean is the bigger your BOR,curls and ect. can be, it can also improve the deadlift, depending on were one stands in thier deadlift.