Hi everyone, audio wiring

I'm new to this forum, although I've been messing around with car audio and electronics for many years. My most recent project and challenge has been trying to get the factory "Alpine premium audio" in my 2014 Jeep Wrangler Unlimited so it actually sounds "premium". Mind you, I do have a budget so haven't been going all out with expensive Focal speakers and what-not, and the big "catch" is, I want to accomplish as much as possible while keeping the factory RHR-730n head unit in the Jeep. Right now, I'm at a point where things sound FAR better than they did and I could almost just stop and live with this as "good enough", EXCEPT I'm still fighting with an AudioControl DQDX I installed in the rear (in a tray above the jack storage area near the tailgate). Basically, I have a JL Audio 700 watt marine type 6 channel power amp under my front passenger seat powering everything, and that works fine (no hiss or noise issues at all). When I add the AudioControl, I get better sound with the ability it brings to EQ everything and to control the level of the bass sub -- BUT I also get alternator whine and hiss/static creeping in. I've torn the whole thing out and redone it twice now, and really thought I had it all working properly this time until the other morning. The weather was pretty cold, so maybe that made a difference. But what happened is everything sounded ok for the first 10 minutes or so I was driving, and all of a sudden, I got a bunch of hiss out of the rear speakers and what seemed like a reduced volume level from the front, driver's side. I also heard alternator whine along with the hiss. If I turned the head unit off and back on, the problem went away for a minute but came back. Today, it was warmer (almost 60 degrees outside) and I drove the Jeep for a short errand. This time, I heard a bit of static and alternator whine coming from all of the speakers during the whole trip (but not that suddenly loud static I had before). I have everything sharing a common ground (bolt through the frame in the front passenger-side wheel wheel). Some people are telling me my ground wire to the AudioControl may be "too long" since it goes all the way from the hatch area to the front passenger wheel-well like that. But the more I read about proper grounding, the more I get the impression that rules recommending an "under 18" long ground wire) are really only applicable to the head unit, for the purpose of not getting interference on the AM or FM radio? For things such as my DQDX, is it true that it sharing the same ground as the power amp would be more important?

I like the idea of linking grounds together to help eliminate ground loops. This does not mean your EQ needs to only be grounded at the kick panel, though. The longer your ground is (especially if it's a smaller gauge), the higher resistance, and the greater the voltage drop across it. Locate a good ground point near where it is mounted. You can always do a voltage drop test across your grounds under load. If the EQ's chassis is not isolated from the Jeep's sheet metal, you may consider this as well. Keep in mind the more components you have in a system, the more places noise can enter. Also, a failing battery and/or alternator will allow excessive ripple voltage. Make sure to check these as well.