Small update because I had a modification of my system. Ever since I installed it there was something about it. It was nice, good even, but not extraordinary as I hoped it would be. Few months ago a noise appeared when engine was running. Barely audible, but it was there. So I set on a mission to see what was happening. First I thought the grounding of HU was not best as it was just hooked up to the factory wiring.
I bought 2,5 mm2 wire and connected it to the same ground and capacitor to give me the same plus and minus for the HU as for the amp. Wired everything and tried it and again the same, the noise was there.
Next on list were the interconnecting cables. Unplugged the front ones, same thing. Replugged them in and unplugged the rears. And noise was gone! No noise with only front speakers running.
So, I am onto something. Tried another interconnecting cable to rule out the cable and nosise returned. Swapped the cables on HU to rule the HU out and the problem was still there, again at the rear speakers only.
It had to be the amp. I knew it was opened as the warranty seal stickers were broken so took from my shelf another one I had lying around. Rockford fosgate 4.6X almost 20 years old 4 channel amp rated at 30 W RMS/channel into 4 Ohm load.
Connected it and tried. It started no problems, and no noise! Everything was OK apart the fact there was no bass at all. My first impression was that is to be expected when you have only 30 Watts pre channel, but a friend of mine reminded me that that type of amplifier uses X card system and it is probably set in HP (high pass, filtering lower frequencies) mode what would explain absence of basses. Opened it and turned the card to full range position and tried.
Oh my God! OH MY GOD! The system CAME ALIVE! That amplifier is playing music beyond description! It is full of energy, controllled, plenty of punch in bass area, warm... This is now playing as I was hoping it would be when I put all those hours in dynamatting everything and routing the cables, selecting the speakers etc...
This is now (finally) one of the best systems I have ever heard and it is in my car :grin:
The amp is now installed just for the time being until I decide what to do. If it stays installed will need tiding up instalation. The other will get repaired. I know it is fantastic as well, but it is not at its 100%. In the mean time, I can just say that 4.6X is incredibly good amplifier and that punches waaaay above its declared 30 watts
Improvement was quite nice when I installed the JBL for the front speakers. Those Rainbow speakers are superb. In fact, they won couple of tests and it is said that they are best what you can get for that money. 
