Interesting settings some of you have.
I have not taken delivery of my GTI yet, nor do I have the Dynaudio Option. However, I have a bit of experience in car audio as I have been installing kit into my cars constantly over the last 7 years and have learnt many things when it comes to tuning.
The first thing that I will always question is why people fade speakers to the rear. It is bizarre to say the least because our ears face forward so bias should be towards the front. The reason for this you should be aiming to create a stereo image as if the band is performing in in front of you with the dash as the stage. When you start fading to the rear, the image is dragged towards the back and everything starts to sound a bit strange.. Tell me, would you go to a concert and face backwards?
IMO rear speakers are there for one reason, if you have passengers sitting in the back. Any other time they should be faded out completely so you can enjoy a more accurate stereo image. The only speaker that should be in the back of the car is a sub woofer, sub bass is non directional so providing the sub is located in a position where there is minimal cancellation, you should not be able to tell where the sub is, you should feel it as an extension of your front stage. You should not be able to differentiate the sub from the front speakers, they should sound like one.
I know by now a lot of you are thinking that I do not know what I am talking about, but I challenge you to try it.. Fade 100% to the front, at first it may seem weird as there is an emptiness in the back but it will not take long to get use to it. Drive around for a week like this then fade the rears back in and notice how bad it sounds as the singer and the band is pulled back behind you.
In 7 years I have run rear speakers in 1 car, which was my first car but I only ran them for a month before I replaced them with a small sub. In my last car, a 2005 STi I had a pair of Morel Elate 6 speakers only running in the front because I could not be bothered with the subs.
Trust me on this one!
As for other settings, they tend to be subjective. I tend to leave all my EQ's on flat until I identify certain frequencies that are resonant, for me this tends to be in the 3-4KHz range so I will generally notch them down a bit.
As for bass and treble adjustments, I tend not to touch these at all.
If you have split components (which the Golfs do) then when you start adding treble, you are raising the sound stage higher towards the level of the tweeters and then it starts to sound bias towards the tweeters and the over power the woofers - not to mention irritating to your ears.
The same goes for bass too and I find that adding bass makes it sound muddy rather than more bassy or punchy.
So as an experiment, fade 100% towards the front and leave your settings on 0. If it sounds bad, I reckon it is your source, are you using a burnt CD made from downloaded MP3's? Are you using an iPod with poor quality MP3s? and by poor quality I mean below 320kbps or lossless. If yes, go and get an original CD and try that out.. Keeping in mind that all CDs are recorded differently so some may not sound better than a cassette tape. You will know a good CD when you hear one, but here are a few I use as reference because of their awesome recordings - not for the song itself!
Bee Gees - This is where I came in - Track 9 - Loose Talk
Toni Braxton - The Heat - Track 3 - Spanish Guitar
Angus and Julia Stone - Down the Way - Track 4 - Big Jet Plane and Track 7 - And the Boys
All of these tracks will test the mid range and top end of your system with amazing vocals and details.
For something more punchy and dynamic get:
Armin Van Buuren - A State of Trance 2009 - Track 1 - Unforgivable and Track 2 - Spring Breeze, play them sequentially.
Jamiroquai - A Funk Odyssey - Track 1 - Feel So Good, listen for the detail at the start of the track; Track 7 - Black Crow - awesome vocals and clarity; Track 9 - Twenty Zero One - test bass response and dynamics!
Have Fun,
Adios,
Emille