So, I instaled the new speakers and the sound deadening material and there's definetly a big improvement over the stock. What I noticed so far:
-a clearer mid-range, even at low volume
-now I can crank up the volume close to 3/4 of the max volume, compared to before when just over 1/2 of the max volume the sound was getting un-listenable; also now at 3/4 of the max volume there is less vibration in the front doors panels than it was before at 1/2 volume
-to start hearing the rear speakers from the front seats,now i have to move the fader more to the back
-an overall better sound
The sound deadenng mat I used is called InPhase Deadquiet and I used 3sheets(45cm x 81cm each) for the front doors, I can't compare it with Dynamat Extreme but I'm pleased with the final result. Also, it was quite easy to install it even if in the end I had my fingers full o cuts. I will definetly sound proof the rear doors, even if I will keep(at least for now) the rear stock speakers.
I'm pleased with the results , is pretty close of what I have expected, but now I want more. I want to change my RNS-D to a 2din aftermaket unit. I like the Blaupunkt New York 800 with Navigation and at around 550E new on Ebay.de it seems really good priced but the main problem is finding a 2din fascia for the 8L A3. Anyone knows where to find one? Is it hard to modify an A4 2-DIN fascia to fit the A3? Will the color of the A4 fascia match with the color of the A3 dash or at least the color of the new radio? Also, will I need to change/modify the original metal cage holder for the new unit?
Here's a pic of my car interior and before/after pics with the a front door panel: