When I sold my X6 i really missed the useful knob, so I started to look for an external one, and incredibly the griffin is the only option available.
So I tought to buy a cheap rubber equipped with a knob to keep just that section.
Then I discovered "volumouse" a tiny free app that one can use to quickly adjust volume and do other tasks with the mouse wheel.
3rvx is a nice optional addition to have the onscreen display