Take a look at post 1 from @Absolut5 above..
View attachment 5945 We do number of tried and tested audio upgrades in the T6 which we have used over the years in T5s but the original T6 headunits respond really well with our signature setup.
These come with a JL XD amp, Hertz front components, JL 10" sub in the original underseat sub enclosures we designed and manufacture.
The sub is controlled by a discreet dash mount rotary control.
If rear speakers are required then we drop a set of coax 2 ways in just to give rear ambience and run them off the headunit.
Other options are available from Rainbow and Blam
Pioneer Avic F88dab is proving extremely popular, using the pro Fit facia, interface for parking sensor graphics and MFSW, and using dash USB retention kit. This Pioneer has the capacitive screen for accurate screen navigation and ideal when dealing with sun light.