More expensive DAC the answer?

I agree that you should start at the source. The distortion you speak of may really be jitter from the DAC presenting as harshness thru the speakers.

Additionally, as I stated above, a hollow sound may indicate that you need acoustic treatment added to your room.
Without any treatment, soundwaves carrying the frequency spectrum, IOW bass, midrange, highs are not being directed to your listening position.

The room is a major factor in reproducing audio. But your primary upgrade should be the DAC/transport digital chain.

Thanks for the great ideas gives me a few paths to follow.

Based on ideas and advice given above I am going to try an Schiit
Gungnir DAC, and go from there.

Your wasting money if the room acoustics are not sorted out..Your going to likely change tone a bit but a "hollow"sound will still be there...

I will also be addressing room acoustics... I think you're right about hollow sound!