For the general benefit of all, I spent 3.99 to get the b-quiet sample pack. I wanted to check out what they smelled like
I'm no audio expert, but b-quiet extreme, b-quiet lite, and brown bread are all closely related. extreme has some indentations in the metal, otherwise it's brown bread. (I guess the indentations are why extreme weighs less) lite is the metal part of brown bread without the black asphault stuff (no indentations). Lcomp and Vcomp are foam, L comp has 2 layers with a thin lead sheet in the middle (pretty cool!) and vcomp has a thick, heavy sheet of plastic vinyl on the back. vcomp and lcomp don't have peel-and-stick adhesive.
Smell test: vcomp and lcomp smell like plastic foam. (What a shocker.) lite has no smell at all (just metal and adhesive) extreme and brown bread smell a little like tar. Smell is stronger I wedge it under my leg for 5 minutes (for heat!), but still not too noticable. But the only place that it smells are the edges: seems like if you use less seams that it will smell less. Also, seems like the smell will lessen as the exposed tar at the seems dry out. Or you could tape the seams--they're naturally sticky.
The verdict: comparing the adhesive-included sheets, b-quiet extreme seems to be best for the price ...however they all seem exactly like roofing materials! I'll try "peel & stick" roofing material from Home Depot next.
By the way, Lcomp is really neat, looks like it'd be good to eliminate engine noise (if placed on the firewall). So basically it's not needed for a WRX... I also don't like the idea of a separate adhesive. Looks to be a good sound barrier though, maybe for people wanting to do the floor. Just not me.