You will always eventually need a better DAC. IMHO all internal DACs are a compromise in lower end components. Bite the bullet and check out a Denafrips Venus 15th. I am sure it will smooth things out. Start at your source and work your way out. @audioman58 sells them for a discount. Run the A6 into it. Get a good quality USB cable too. Next consider speaker upgrade down the road. Good luck.
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.