Here is a site that makes enclosures that fit into the sparetire well: http://www.subarusound.com/subarusound/default.asp

I was thining of losing my Infinity Basslink and going with a 5-channel amp w. unpowered sub (maybe in the spare tire well).

This company makes sub enclosures that fit on the side of the trunk for anyone that wants to keep their spare: http://www.geocities.com/subee_sound/main.html