Have you kitted out the car with ICE yet mate, personally i woudnt bother with all that sound proofing.......the newer clios are pretty good acoustically anyways. Put the ICE in, listen to how it sounds for a week or two at different volumes with different types of music, if you feel it needs some extra sound proofing then go and get some but dont buy it unless you really have to.
My ICE consists of: Alpine 9812RB MP3/CD, MB quart front comps with separate crossovers, MB quart 6x9s in "Auto acoustics" steath shelf, MB quart 10" sub in sealed MB quart box all being ran by a Genesis profile 5 amp.
Ive no sound proofing what so ever and it sounds really really good.