IMO line level converters are sh*t, I've had a cheap one $50 and an expensive one $300, your best bet is to get an amp that does the converting itself (my cousin has one in his subaru and it HAMMERS, all up cost $700, amp, sub, box and install from JB, JL audio gear) or get a aftermarket head unit, which I have, and can muck around with heaps of settings, iPod connectivity, USB etc..