I've just today bought a Mark Grant Y-Sub cable, but I'm now getting a little unsure if I've bought the right one? There are two inputs on the back of the sub left and right and and two on the back of my denon 3805. Do I need to use both on both units? Has anyone else got a similar set up that could share some 3805 sub setup tips with me our is it just as easy as plus and play? Thanks, Devs.