The cda 9887 should have 4volt pre outs.
There is no need for a line driver at all, even if your headunit had 2volt preouts.
Simply right now the line driver is causing more harm than needed.
Two ways to fix this would be:
1: ditch the line driver that is not needed.
2: turn your headunit volume down to a level that does not cause distortion on the amp due to the line driver.
Your problem just proves linedrivers are not needed ever (unless you have a setup and your running like 6+amps from 1 set of preouts).
I'm pulling the line driver out now to see how that goes. thanks for the input