Re: Anyone ground the HU twice?
Some of the factory harnesses just wire into a common ground. This is the type that would give you noise, or sometimes clicking when various devices kick on.
If you have noise, then I would switch your ground from the harness ground to a dedicated ground to bare steel behind the dash.
'65 VW Bus
(2) PG Ti 12's, (2) Aura Sound 8's, (2) SoundStream 6.5 coax, (2) Alpine Type-S 6x9's [rear fill], MBQ DSC1500.1D, RF 501X
'02 BMW 330xi (AWD coupe)
Harman/Kardon 12-speaker System Option - sounds good =)