Suggested upgrade paths

So, I am looking at spending 5k to improve the sound of my very modest system. I currently have a Rotel 1592. Being fed by an Eversolo DMP A6. I’m using the Rotel DAC, as I didn’t like the ESS DAC. This feeds a pair of Wharfedale Super Lintons. 

While it sounds ok with the volume at 60-65. If I want it louder, the treble is shrill to my ears and the bass not as clear/punchy as I prefer. I run the bass at +3. I am considering purchasing a subwoofer, along with a DAC/DDC. 

The room is roughly 450 sq ft with 10’-12’ coved ceiling. Looking for upgrade path suggestions for the mentioned 5k investment. Thanks in advance.