My Custom Audio Install, 2017 Prius Prime Premium

Recently purchased 2019 Plug In Premium and very interested in this approach, I have a 600watt JL audio mono amp and 8" JL audio sub I would love to integrate into the Prius.

You mentioned adding a 2nd stereo, what unit is this, where is it installed and how is it controlled? Also would it be possible to run an 1/8" stereo cable so that an analog connection could also be utilized to that 2nd head unit in addition to bluetooth. Thanks!