Im trying to put an amp and subwoofers in my 2018 accent sel and cannot find any one that installs them. I was also thinking about a line output converter. Does anyone have any advice/info on installing a amp and subs to factory stereo on my Accent

 

Something you might consider.
Most new vehicles these days operate with networks. These networks have several nodes/modules that are part of the network and some new vehicles have the radio as one of the nodes in the network. I don't know for sure if your vehicle is built with that system, which if it is, doing anything involving the radio can produce a "No communication" problem and the worms are now out of the box. So,,,,,,,,,,,,,I would suggest that you check with your dealer service dept and confirm if it is permissible for you to install any addl equip that could affect the network operation.If this can save you some grief, it will be time well spent.