I hate having a nice car with a crappy sound system, and these cars honestly are pushing 20 years old now and they just need to be refreshed.
here is a video about how I made my 997 gt3 with the ASK amp and 9 speaker sounds system perfect.
links
Amp / wiring
$150 KENWOOD 4 CHANNEL amp – https://a.co/d/gEL14GZ
$84 MOST 20 Pin connector – https://technicpnp.com/product/logic7hkepsindividual-audiobang-olufsenbowers-wilkins-most-oem-amp-replacement-hardware-kit-for-most-converter-applications/
car harness wiring diagram – https://www.6speedonline.com/forums/997/317415-ask-amp-replacement-diy.html
$1000 9 Speakers – https://www.scrdistribution.co.uk/987—997-9-speaker-audiofrog-upgrade-kit-15654-p.asp
head unit options
$1300! PCCM+ – https://www.suncoastparts.com/product/sku997pccm.html?gad_source=1&gbraid=0AAAAADnpVeRdg9m4e-hO9x1Ky7oHR0G1g&gclid=CjwKCAiArKW-BhAzEiwAZhWsIDoxrLBItkm8U6JRK4oiMhIYevfpcYP6n6kuxvd6KU4VyymDelopxxoCI6QQAvD_BwE
$200 Aliexpress head unit – https://www.aliexpress.us/item/3256806728725659.html?src=google&pdp_npi=4%40dis%21USD%21339.76%21180.07%21%21%21%21%21%40%2112000038714391173%21ppc%21%21%21&src=google&albch=shopping&acnt=708-803-3821&isdl=y&slnk=&plac=&mtctp=&albbt=Google_7_shopping&aff_platform=google&aff_short_key=UneMJZVf&gclsrc=aw.ds&albagn=888888&ds_e_adid=&ds_e_matchtype=&ds_e_device=c&ds_e_network=x&ds_e_product_group_id=&ds_e_product_id=en3256806728725659&ds_e_product_merchant_id=109234012&ds_e_product_country=US&ds_e_product_language=en&ds_e_product_channel=online&ds_e_product_store_id=&ds_url_v=2&albcp=20546179816&albag=&isSmbAutoCall=false&needSmbHouyi=false&gad_source=1&gbraid=0AAAAAD6I-hF2HSwK-qv063jipHDW8156Q&gclid=CjwKCAiArKW-BhAzEiwAZhWsIDJbCPIOmHgKLc6WFE6ac_mJKoaot_-uZVy4lQlpu78rzwTp-fCAchoCr5oQAvD_BwE&gatewayAdapt=glo2usa
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Taking pos from one channel and negative from the other does not give you a good center channel signal. It gives you a signal , but not a good mono. It will sound very odd and distracting. Ask me how I know