My son & I just installed the KMR-D562BT with the Metra 70-1786 on Saturday (exactly per the GregWork's post, the Metra uses the speaker outs, no line converter) (and snapped in only the bottom of the trim ring, looks great) in his 2004 Limited coupe and were very happy with the result - we feel a significant volume gain (and better fidelity) over the stock Infinity w/o Nav. It WAS easy! We checked our subwoofers and the foam surrounds were still good. I'm guessing the VW01B is exactly the same as the Metra (a speaker-out harness), just different manufacturer, so no benefit to switching those out. Perhaps the OEM amp is not receiving the turn-on signal (or mains power) or has failed...

I just wanted to reinforce that the forum-standard Kenwood direct speaker-out connection to the factory amp works great. Or should We find 30-35 volume unbearable for longer than a few seconds.