Help running line out converter

Hi everyone im going to be doing stereo install soon but i want to keep from cutting modifying the stock system as much as i can. dont want to pull out the radio

I've ordered this 4 channel adjustable line out converter and was planning on removing each door panel and soldering extended speaker wires from the solder spot where the factory hyundai speaker is connected to. i want my loc in the trunk so the gains on the line out can be adjusted easily

NVX XPLOC4 600W Super Low Distortion 4 Channel Adjustable Line Output Converter | eBay

***MY PROBLEM - my line out needs a constant power, remote turn on (where and what would be the easiest way to get these)***

i would then hookup my rca > 4 hifonics channel amp > run speaker wire back to every door to my rear
- alpine sps-610 coaxial (80rms)
- polk champion mmc65000 (120rms)
-2 12" Kicker L5's on 2000w dhd amp

***For my 4gauge amp power wire i was wondering if it would fit through that gloveblox gromet, it may be tight (i used it for my fogs)***

planning on insulating the doors and using the factory speaker bracket i do however have rings made for my front components

Let me know what you guys think or if anyone has a easier method