Be careful in attributing any of this perceived "glare" to your DAC. You're going fully digital directly from your computer (into the DAC) - which might not be ideal.
Your specific chain / your AMP / tubes / power, etc all play a role ...
A USB improvement should reduce noise. Digital noise tends to masquerade as added warmth. An improved USB input should provide a "cleaner" signal which could be perceived as more neutral - again, all very subjective.
As we discussed over PM, the Wavelight does best with I2S or AES, so consider giving those a try when you can.