I used RCA splitters on the rear L/R pre-amp signals to split it to the 4-channel amp and to the powered sub which has both line or speaker level L/R inputs. No external crossovers needed, the JL Audio powered sub has its own low pass filter.
I just used an oscilloscope to adjust the gain up on the rear L/R channels to compensate for the split.
Hey, I got the system working! Thank you for all your help! It was a plug and play experience (with some hiccups) and with your pinout information everything worked on first try! I will probably make an easy step by step post guide people who just want to upgrade the amp. The sound is AMAZING, but I may have to get some inline filters or fine tune the amp more (The midranges are boomy where voices can sound abit bassy.)
The X1 adapter ran a little small for the X1 connector on the chevy bolt. So I took a dremel and sawed the bottom of the X1 connector (on the harness adapter, not the OEM plug) to make it fit, and it worked perfectly (sorry forgot to take picture of the sawed adapter! but it was really easy to do with the right tool). Since this X1 connector is fused at 14.4V 25A I can get 360W max which proved to be more than enough for the whole car. No additional wires needed.
Added a bath towel and put the amplifier under a plastic bag for waterproofing just incase water wants to find its way back in.
SINCE the amp is rated as low as 2ohms, I combined the Left Rear Channel with the Left Front, and the Right Rear Channels with the right front. So Instead of running 5 channel I am running 3 channel, (Left, Right, Sub). Sub is bridged to channel 3 and 4 for extra power at 4ohms while the Left and Right run parallel on channel 1 & 2 at 2ohms. Picture is attached. This made the process a whole lot easier to deal with without getting anything additional and keeping project cost low. The amp, especially being bridged, has more than enough power to run the stock sub and hit good bass especially at high power.
Max volume 63 is extremely loudddd, yes!! lol
The sub was at half volume sensitivity on the amp setting while the left and right channels were at max, but the sub still comes in strong even at half power!
The midranges are boomy, the amp settings cannot low pass filter more than 200hz. Most likely will get 600hz inline filter for the high and low pass to balance everything out
I will I do some additional tuning on the amp to see if this is actually required. 200hz shouldn't be so boomy. I lowered the bass from the head unit but this also lowers subwoofer output due to my setup. I will probably boost channel sensitivity for channel 3|4(sub) and lower sensitivity on channel 1 & 2 to balance it out first before I buy anything. Will confirm in another post
*Just realizing since the head unit is 4 channel, it probably doing directional sound for each speaker. Thinking if this can affect performance and if I can adjust this to a more stereo feel
Thanks again for all your help @tk1971
. I will include your name in a new post when I make an easy step by step guide for people who want or need to replace their amp. The sound is AMAZING. Still all stock speakers and tweeters, but its really loud and maintains clarity. I am an Uber driver and a lot of passengers were really impressed.