If you have the XXV-01D, then you might as well get an XXV-03A/KAC-X811D/KAC-X812D.
I know kinda contradicting what I just said, lol, but that's actually another reason I decided not to get that amp myself. I figured it's a nice amp but there's better out there if you spend a little more and the extra features like amp control I wouldn't be able to use anyway. I'd definitely have bought one it if I had a Kenwood HU, but I don't...
And as a slight correction I think the Kenwood will actually do more than rated into 4 or 2 Ohms, it's at 1-Ohm where it just makes it's rated power. I.e. it will do more than 400W and 800W at 4 and 2 but it just reaches 1000W into 1 Ohm (from the review I read anyway).