Re: 8 inch
The 8" speaker in your rear deck is a subwoofer, not a midrange. If you want to replace it with a mid range driver you'll also have to get a signal from another output, as that output is crossed over below midrange.
And if you install a single driver tapped into the right or left channel, you'll kill your stereo separation as well as making the other audio channel's audio much less audible.
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