I just bought 2 Rockford amps off a guy on kijiji

I bought 1 Rockford Fosgate Punch P600.1bd and a 4 Channel Amp i dont remember the model number.

Im using a line output converter to the 4 channel amp and using the passthrough to go to the 4 channel amp to the subwoofer amp. But the problem is the subwoofer is barely making any power and my old amp was making much more power and it was a very shitty amp that clipped alot.

Im using 2x 8 Gauge wires for each amp and i think 15amp fuses at the battery.

The second issue is that im hearing some distortion from the tweeters. I feel like somethings wrong with my wiring. I have all the cables running on one side of my car and im using alot of speaker wire of different sizes. But i never had an issue on my old amps and subs


My subwoofer is an MTX Thunder Pro2 500w RMS


Please help i dont know what to do I feel like just bringing it to a shop