you dont want amp to be on 24/7. Or some even dont want it on when car is started. My amp goes on only when the head unit is on. but if you dont drive much, i guess you can have it at any 12v that turns off when ignition is off.
i have 1 10" eclipse sub in sealed box in back, with a OK kenwood amp ( replaced my old amp that broke).
The line is tapped into the rear stock subwoofer and converted with 'line output converter" if you have aftermarket head unit, yo dont need to do it that way.
speakers etc are all stock. Sounds good for me. I just needed extra bass in back thats all.
Only complaint is that part under the back windows shakes from bass. Would need to dynomat it all , but too much trouble to go through. Licence plate shaking too ( going to put dynomat for licence plate soon).
Thats about it.
Where do you connect the line output converter? Back of the head unit or off the subwoofer leads?