if you have auto stop start in your civic, you will also need a ballast to counter that, they not silly expensive (under £100, connects2 do them also), new 9G fascia (connects2 have em) and their steering wheel adapter, plus reversing camera convertor isnt cheap either.
last time i checked it was around £250 for the parts to fit it, plus head unit plus speakers plus an amp (i have a 4 channel JBL spare atm) but even without amp i was looking at £900 (£300 plus £300 plus £300 speakers for 4) for items last check. also if your not comfy running a direct 12v fused feed form underbonnet to boot for the amp and earthing to bar emetal for sub in boot, then also factor in £90 to £150 for a autosparky to run a new pro feed to boot.
that was all JBL and a Pioneer higher end DAB head unit with Android car play, when my garmin subs expire i will consider it for betty, till then ive got it sounding decent with some optimisation of my sources via Acid pro etc and recoded to suit the Honda setup.
also a major flaw in iphones with hondas with audio quality, connecting with the usb limits the codec used to barely CD quality (44.1Khz), connecting to bluetooth (usually handshakes around 48khz) DVD quality.
It allows the device connected Sound codec to use full bandwidth that usb cannot provide while auto-charging
thats why even cheap bluetooth speakers always sound so clear and punchy
its in the dynamics of the sound and the hardware RAMDAC in all devices, same applies for the stock unit.
Make sure you have volume levelling set to max and set balance and fader to dead center, Honda in their "infinite " wisdom made the rear speakers ambient mode and not actual true rear versions of the fronts.
replacing with a 3rd party unit and amp removes Hondas "ambient mode" when you rewire.