Thanks guys. Thing is, with a different head unit, the amp works fine. Ultimately yes thats the solution, get a new head unit, but right now there are more important things to spend the cash on.
I could throw the small amp back in, but man there is just not enough power to push the dvc. So running it in svc is allright and it give a decent enough low end, but nothing like the class D.
Strangely, my volvo gave the same trouble... and I thought it was the stupid fibre optics in the car.
Thanks for the comments guys! I appreciate it!