Sound insulation

[Vex182]

I've always thought the S3 was a quitet car for it's ages compared to similar aged cars of its size (mk1 focus, 306, Astra etc). I'm hoping to drown out a little bit more of it. I reckon most is from the tyres and the emgine still so thinking of trying something of this behind the wheel arches and possibly behind the bonnet padding. Anyone done anything like it?

http://pages.ebay.com/link/?nav=item.view&alt=web&id=251336537711