Soundproofing Yaris as a gift // Help!

[duck]

dynamat is like kleenex, more expensive then just regular tissues, just as good though, but you'd probably still buy the brand name.

dynamat is sold in sheets that one can apply around the inside of the trunk, underneath any fabric.
one can go crazy and just put it everywhere, but it's fairly expensive. the best way is to find any points around the subwoofer that might rattle or provide room for the sub to move and just cushion those areas. May take some calculation or trial and error, but it makes the most of the least.

dynamat is also sold in a license plate kit. you might be surprised how much noise comes from the rear license plate shaking around with a subwoofer in the trunk.

personally i just buy good quality subwoofers and don't turn them up to "booty bass" levels, but if I ever did want to go crazy, I'd buy the dynamat stuff.