Arc Ultra with Powered B&W Subwoofer

I have an outstanding B&W Sub.  Could I use Arc Ultra and synchronize it for home theater?  Or could I use a Connect with Sub-Out to the powered sub I already own?  

If not, has anyone placed a Sub3 or Sub4 in an enclosed box under a TV?  I want to build the sub into the wall cause my wife insists it will not be in the room...