@audphile - I do not use the TWL power cables currently. The speaker cables do not run bright in my system. I used the mapleshade double helix for a short period to test and THOSE were very bright. They were very open, but the brightness with those was quite pronounced to me. The TWL by comparison is full and much more natural to me. Granted, I do indeed have SET amplification and a tube line stage, so it works well together. This pairing was done before I made any DAC changes, so introducing the DAC is what introduced the 'complaint' over time.
I agree about the upsampling. Just not where this DAC shines at all.
The brightness is slight usually, but there are occasions where the top end distortion is pretty rough to where I need to turn down the volume quite a bit. Some of it can probably just be chalked up to mastering on those particular albums for the here and there borderline unlistenable distortion, but there's always an underlying 'treble bias' regardless of what mode I use or files I listen to, exacerbated by using upsampling or with bad recordings. If I had a streamer with a coax output, I would try that input instead, since it may be just be a case of the DAC's USB input not being great, but I don't currently, which is why I stressed optimization for USB input on my original post.
Got some interesting suggestions so far. I also got some DMs mentioning some things as well, so some good starting points!

