I just put on a new Western Ultra mount plow, and I was looking at the pictures of the DSS, and I was wondering the same thing. After installing the plow mount, I am not sure it would work, unless you mount the DSS over the plow mount brackets. I was not to overly impressed with the fit of the plow mount, I had to enlarge 2 holes on the mount, and until you tighten it down, it does not fit to well. Like the instructions said, Do not tighten any fasteners until told to do so.
Just my $0. 02