Been looking into sound deadening the boot and doors etc of my IS. Ive upgraded the speakers and have a small sub running in the boot. I always see good things about sound proofing on sites etc but dont know anybody thats actually used any of them? What sort of difference does it make?

I dont mind spending more money as long as it makes a decent improvement?

Also, theres stuff on ebay called SoundX which is really cheap. any1 used this at all?

Still 50/50 as to wether im gonna bother with i. just thought id see what kind of feedback i got.

I voted for DMX as it's what all the ICE heads use. I planning to get some for mine when I upgrade the fronts. It's definitely worth doing. Cuts out so much road noise & improves bass response

I wouldn't go for something which is only in the name automotive related.
Avoid cheap crap and focus on butyl based products.
The thickest I have found was StP Gold (2.5mm thick 17sq ft at £55)later on StP Silver 2.2mm thick (only available in bulks), next would be damplifier pro 2mm thick 16sq ft @ 75quid, next should be Dynamat Extreme door kit 12sq ft at £80 - 1.7mm thick, last one in that chart is FATMAT Xtreme 1.15mm thick 20 sq ft - £65
Hope it helps

I used Dynamat in the past now my vote is for the stp