You can continue to run your factory head unit with aftermarket components in a VE Commodore, by using an Alpine KCE 431R Converter. Make sure you apply Dynamat to the doors and boot to both enhance sound quality, and prevent road noise.
We used Alpine Type R 6.5 Splits up the front, Alpine Type R Coaxials in back, and an Alpine Type R Sub and Box running from a Alpine V9 5 Channel Amp in the boot. The sound is outstanding.