Scopesys....u did exact what i did... hack the head unit, install jet audio app, use a big thumb drive with high resolution flac files... change out the speakers with quality speaker and it sounds good.... rears dont have any output compared 2 front...cant even hear them from the front seat...
finally tested my 2017 Honda Civic Si with PRL CAI, downpipe, frontpipe and Hondata +6 flash...raced a Subaru WRX STi when stock and took a hellova beatin... engine fell on its face at 5600 rpm...new setup was still pullin hard at 6500rpm and dyno charts say 2 7000 rpm....great $1700 mod