As you know I don't know much, but I will share this. A local installer insisted I needed a line driver. I said "My HU is 4 volts... you really think I need a LD? I said years ago I think they were needed, but not these days. I understand they can introduce problems if they are not needed." He was very cocky, blew me off, and insisted I needed it. Knowing you can get one for $100.00 or less I said... "Well maybe I will get it, but if it's going to be $600 or something crazy I can't do it." He then said well that's about how much it will be. He was just being a butt. I did have a sub fry an amp recently. At first I thought the amp was the issue. Got the same sub and amp replaced and the same thing almost happened again. The amp was going in to protection mode this time. In the end it was determined the sub was messing with the amp. The sub was replaced with another brand and all has been well since.