I have not regrounded the head unit yet, but I never had any noise problem with the previous radio. The radio is grounded through the car's harness but I may try to ground it to the chassis and see what happens. I think I checked the resistance of the ground a while back and it read 0.00 ohms though.
Big 3 might help but then again I wasn't having any issues prior to installing the new radio so I'm skeptical about the results (I know it would be piece of mind though, might do it eventually for the heck of it).
I did readjust my gains when I installed the radio using the multimeter vo