u/Able-Jacket3586

Not sure if this is the correct subreddit for it but currently I have a FLX4 getting audio from my PC via USB-C. My FLX4 RCA output goes to a Fosi Audio powered amplifier(BT30D) which outputs to a subwoofer (PSW10) and both my Polk Audio speakers(T15) via speaker wire. My question is I use this set up in my bedroom for DJ and watching movies. Is there a way to integrate a surround sound system into my current setup? If not would adding extra passive speakers to my setup be as simple as connecting via the subwoofer speaker outputs? Also if anyone has any suggestions in upgrading my setup i have a $500-$700 budget I would appreciate it. Thank you.