I don't have panniers like you.
I have to carry my work stuff and a backpack every day, so the box is really necessary.
When I go out for fun I leave it off and wear a "bum bag" - big enough for phone, wallet and camera!
I have an SW Motech (German) rack which is really cool and cheaper than the Triumph rack. With the correct adaptor plate, all the Givi and Kappa luggage will fit.