I suspect that we could run 2 B3s off of one APW3++ the same as with L3+s. (Or 1 B3 and 1 L3+). For a while they made a special version of the APW3++ with extra connectors specifically for setting up 2 L3+s on one, but they dropped that from production. However, it's only the connectors that are different so if you get a pack of cheap splitters it should work fine on a B3.