Calo was a bounty hunter and pretty skilled and smart, he did kill a rancor using a thermal detanator, he found his way of Taris even when Revan and co took the Ebon Hawk, which is just a surprise if you ask me, because how the hell could have have possibly pulled that off? The guy is pretty impressive, but i'm still guessing Boba wins. He has superior armour probably equal or better weapons and well just don't know enough about Calo to call him equal to Boba.
Nord was the greatest or second greatest bounty hounter in his time. And if i'm not mistaking Cassus was invented by Kotor and killed in the same game, or actually before the game. You can't even be sure he's related to Jango for that matter. He's nothing.
Boba would take Calo, to say Cassus would do the same is talking out of ignorance.