This is why people like me exist!! As long as questions are asked we can help. To understand gain, you should understand circles. Graphing a signal equates to a "sine" wave...like in Math. If you're acceptable amplitude(height of graphed sin wave) is between say .5V and 8V...then the "ceiling" for acceptable signals is 8V. Anything higher than that is cut off....and instead of being a wave...you have boxes...or square waves. If you read more about speakers and signals you'll realize that a square wave equates to playing a tone to some extent. That is NOT good. That's as much as I'll say about that...
If you're "output" from the HU is 4V...then gueestimate where that is on your gain and leave it. Don't touch it. Leave it alone or blow something up.
I'm not saying you did...but typically people presume that money equates to some standard/status. Sorry if it came out wrong.last post, i didnt dump a ton of money.
i actually got everything besides the deck brand new for under $400. which would include, a 12" kicker l7 with correct sized box, 2farad cap, 0g wiring kit, and a boss dd3600 amp. ive got someone off craigslist willing to trade me a JVC Arsenal KD-AR800. Ive been told that the arsenal line of JVC is pretty good. based on the specs off crutchfeild would it be worth trading? Just trying to get my system to sound the way it did when i had my stock radio, which was awesome. JVC Arsenal KD-AR800 CD/MP3/WMA receiver at Crutchfield.com
Before you take another step....change the polarity to your subwoofer. Meaning, change your pos. and neg. wires on the speaker terminals. See if that helps
However, the Arsenal line is pretty decent from what I gather. I'll have to go read up on that...