Your soundbar has zero way of sending audio OUT to anything. It only wants to take audio IN.
Thus as audiophile there is no way to get data to external speakers from the soundbar.
You can do as audiophile said and split the sound input and extract the sound, then put into rca/3.5mm format and go to powered speakers.
You can only have 4 speaker stereo, and not surround sound this way, and odds are it will sound worse and not better due to different volumes and good possibility of a slight delay.