I kept my amp and replaced all of my speakers with Pioneer and then later replaced my HU with Pioneer. I am very happy with the results. Replacing the door speakers with 6.5" speakers definitely improved the bass response. I do get some mids and highs through the door speakers with the stock amp although they are not as clear as the dash and rear speakers.
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2001 Boxster S Lapis Blue
TS Cat Bypass Pipes and exhaust
iPad Mini Dash Install
DEPO Tail Lights