Yes and I did a FULL System Upgrade - It was Mandatory. That Crappy Beats system was Absolutely Unbearable!!!!
JL C3 6.5 Rear
JL C2 6x9 Front
2 JL 12W3 Sealed Enclosure Rear
PAC AUDIO 5v Interface AP4-CH41 -
https://pac-audio.com/catalog/amppro-amplifier-interfaces/ap4-ch41
JL XD 400/4 Mids, Highs
JL HD 750/1 Subs
JL Bass Knob
I used the JL FIX82 in the Beginning, sounded terrible. The digital output from the Beats System is just a dirty signal.
I also used a AudioControl LC7i 6-Channel Line Output Converter with Bass Restoration and that also sounded like crap. Again the tuning is just not right with the Beats system.
I have a JL Audio tuner as well that was used with both of these installations and the PAC AP4-CH41 did the best job
The only speaker I did not amp was the center channel. That Center Channel Speaker needs to stay with the beats system for use of the BT PHONE (You will lose it otherwise.)
If you just want to add subs just use the PAC AUDIO 5v Interface AP4-CH41 -
https://pac-audio.com/catalog/amppro-amplifier-interfaces/ap4-ch41 its a 5V signal and works perfectly