Second that! Dont go cheap especially since the LOC already is the weakest link in the system chain.
Do not use LOCs with transformers in them, they are typically the cheap crap you find at walmart of auto parts stores. Also well known names like Stinger, Scosche and PAC make them too and they are slightly better but not what I would use.
Soundgate makes the best units out there but they cost the most. Imagine that! I used these before and there is zero noise and very little loss from these units.
Type 1 Line Output Converters - SoundGate.com