Lol you've done the hardest bit!
Surely you can find a hole behind the dash that leads to the raadio
Maybe you should have gone passenger side and behind the glovebox?
If it's a similar design to the mk2, otherwise you might have to hide the wires under the dash
I ran power, remote, RCA and speaker cable all down my passenger side with no interference what so ever. Just make sure it's good quality shielded cable
I had an 1800 watt sub, and had power, RCA and remote cables all down the passenger side in my mk3, was no interference at all.
Under/behind the glovebox theres a hole that leads to the head unit wiring.