i recently put 6.5 inch pioneers in my 2000 sports soundbar.  the highs and mids sound great, but the bass you can feel vibrate in the body and rearview mirrors, but you can barely hear it.  is this due to the direction of the speakers in the sound bar or are the speakers too compact in the soundbar?  i dont need exterme bass or anything but you can barely hear the bass and the way it vibrates the rearview youd think it was quading  i am not an acoustics major any thing will help.  

generally, the bass works best if those speakers are mounted low  

http://cgi.ebay.com/8-AMPLIFIED-SUBWOOFER-800W-CAR-SUB-ENCLOSURE-BOX-AMP_W0QQitemZ180239123495QQihZ008QQcategoryZ32822QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

copy and past this link above . i have one of these in my jeep and it fit under my back seat and i have more base than ever it kicks you can even adjust it from little to alot . also you loose no valuable space. you can get good clean base and use you 6.5 for what they are made for witch is mid and highs. if you want pics. of mine installed email me @ djallen30@aol.com