well seeing as i'm a pikey sod...
i sound deadened mine and the wifes yaris quite a bit

i used a couple of packs of dynamat, but was gonna work out massivley expensive, so i tried roof flashing on a roll, and its cheap as chips, tenner for 10m x 300mm i think? from wickes, bq etc. Banged in 2 or 3 rolls in each of the doors, and a 30 quid roll of cheap sound deadening. and it improved the bass quite a bit, nothing like a sub but improved what i had no end (dls coaxs in the dash, alpine coaxes in the doors)
then i went a bit crazy with it...
