Additions, Upgrades? Any advice greatly appreciated :)

I have a Technics SL-D2 turntable with a Sumiko RS Oyster stylus, Pioneer SX-600 receiver, and Paradigm Micro bookshelf speakers. The whole setup was a gift from about 10 years ago, when I started getting into collecting vinyl. It's served me well over the years, but I just discovered this sub, and I'd love to give my stereo a glowup. I listen to a little bit of everything, but a lot of house, techno, and hip hop, so I was thinking a sub might be a nice addition. But, my receiver doesn't have a designated sub out, or LFE, so I'm not sure what will or wont work. However, maybe I'm better served just upgrading the speakers and I can get richer bass as well as all around better sound. Not looking to spend more than $500 US. What do y'all recommend?