OK I can probably help you guys understand this issue with an aftermarket sub in the refreshed s and x and the new Li-Ion 3 and y. It will the same issue across the board. All of these variants will required a secondary battery. Maybe with a lower powered amp (150w)you might be able to get away with it. The Li-ion battery in these vehicle are great for durability and reliability but not for inrush current and relative small storage capacity which isn’t good to run amps. I believe the LI battery capacity is around 6.9 Ah vs 33 Ah on the previous Lead Acid battery How do I know, I’ve had to replace my Li ion battery because of trying to install a JL HD750. After talking with Matt from the YouTube video above, I’m going to give it a go again but with a secondary battery and a battery isolator installed I’m also going to fuse the secondary battery from the primary battery with a 30 amp fuse as . This makes the install process a little more complicated but it shouldn’t be that big of a deal.