Laid back DAC under $800?

It varies but the area that most people find tiring is around 4.5khz you might try putting a slight notch there say -1db. Leave the rest alone and try it for a while if it's  a little better but still to much try -1.5 in that same area. Don’t increase anything without adjusting headroom down a few dB.

Here's a cheat sheet to give you an idea of the different frequencies and what they affect.

https://cheatography.com/fredv/cheat-sheets/eq-tips/

Thanks. I also use Foobar and Audirvana. 

@jtcf you mentioned wire. Do you notice much difference? What do you use? 

OP,  It might be wise to "borrow" or test a couple of different speakers to see if you respond differently to another option besides the Vifa Radiator Ring tweeter in those Onix.  Perhaps a silk dome or ribbon implemented like the Golden Ear? A free test is never a bad idea.