http://www.carbuilders.com.au/ Brendon Carrol is the boss/owner is very approachable and helpful
I have a Falcon ute that I stripped cabin down to interior shell, then started using this stuff. Every nook and cranny, skinned my hands and arms, But its bloody brilliant. Shutting the doors you now hear a solid chunk instead of a tinny bang, Ive seen other Falcon owners get out, shut the door then look back as if something strange happened.
There iare different products sound deadener and sound insulation. For underneath the ute, up on hoist all wheels off, cover brakes and suspension bits then used 5 cans of SuperCheap Auto spray deadener.
The only down side is you now go listening for wind whistles and stuff. Ive used it around mirror knobs everywhere,
How does it compare to Dynamat... Who really knows the only way would be two identical vehicles done exactly the same way with both products. Remember if its cheap on Ebay its a cheap product. You want quality you pay for it.
I am not affiliated with them but looking at a Hyundai ILoad van for business and the first thing that will happen is a complete cabin strip down and 2-3 days slowly with this stuff.