I understand completely. But as peak voltage in hifi is 5v --> low level 2.8v input; similarly 30v peak eps voltage into 15v input is about the same. Bottom line is that as long as you dont turn the volume knob up the last few clicks, you wouldnt get clipping. I cant be sure it works the same on low level vs hi level but i cant think of a reason why it wouldnt.
One way to find out. Ask andy over on diyma
FS:Sub Amp - works w/ Technic harness! MRD-M300 - cheap