I was going to buy the ws-420 this week but checked on the Wetsounds site and noticed that the pictures for the 420 had changed. It looks like it's now the 420SQ and has 3 zone controls. I assume the 3rd is the sub? It also looks like they added a main volume control knob. Has anyone heard anything about this or used it yet? I really like the idea of the sub being able to be controlled separately as well as the main volume control but wanted to see if you guys knew anything about it first...