There are many reasons why you can be experiencing fatigue. The DAC to amp/preamp matching where there’s sn impedance mismatch, interconnects from dac to pre or amp (I’ve experienced fatigue with few cables until I found what matched perfectly), DAC itself can emphasize presence region and annoy you, room acoustics, etc.
Your DAC output impedance is 150 ohms which means the input impedance of your preamp or integrated should be at least 10x that and preferably more. If the amp has low input impedance the balance shifts towards higher frequencies as the bass is reduced. Keep this in mind now and in the future when you select a new DAC. Solid state DACs will typically have lower output impedance and match better with most equipment. Just something to think about
Don’t get too hung up on DACs that sound like vinyl records. They don’t exist. Find a DAC that is better and more evenly balanced top to bottom.
In your price range you can find a used MSB Discrete if you’re patient. Or try Bricasti with severa filter options to relax the presentation a bit.
What are your cables? Brand and model?