I spent some serious seat-time with a Rega P3 outfitted with an Ortofon Blue 2M. played, first, through the phono stage of a McIntosh MA5200 and then, through the phono stage of a Luxman L-550XII, using Focal Aria 536 speakers and clean, well recorded vinyl. That experience was about as far from fatiguing on the ears as possible!
Keep in mind that Rega's TT design and engineering philosophy is predicated upon producing very light weight, low mass TTs with very stiff bracing. As such, take heed of what pindac is saying here. All TTs should be placed on rock steady, isolated surfaces; Rega more than most.
I'm not familiar with the phono stage or the cart you are presently using. If I had to guess, which I'm loath to do because I much prefer speaking from personal empirical experience, I'd say one or the pairing of both of them is the likely the culprit for the ear fatigue. Speakers are part of the pairing equation, as well, as these are the business end of every system. Everybody has to play nice together.
After further research into my TT quest, I eventually whittled down my choices to a Rega P6 outfitted with an Ortofon Black 2M and MoFi Ultradeck with MastertTacker. I went with the Mofi Ultradeck+M and couldn't be more pleased. If you're interested, there's a full review of it in Stereophile (and other places, of course) that, as I recall, Herb Reichart wrote several years ago. Basically, he came to the conclusion, at that time, that the Mofi Ultradecks+M was the best he'd heard under 5K. I'm sure SOTA is an excellent TT. I've just never heard one.
I'm not familiar with the DAC you are using. All I can say in this realm is that I've never heard any digital set-up, even those approaching 6 figures, that my ears preferred over a good, comparable vinyl set-up. This debate over whether digital systems are better than comparable vinyl systems is fast becoming the replacement debate for whether multi-thousand-dollar cables & connectors "sound better" than those costing much less. Sure, digital is much easier, much more convenient and doesn't require the care and attention that vinyl does (i.e. clean records). However, in those direct, structured and controlled A/B shoot-outs that I've done with digital vs. vinyl, even digital systems costing much more than vinyl, I know what my ears like. Maybe it's all neuroaudiological. In the end, your ears will know that they like, as well. Listen & demo as much stuff as you can and let YOU'RE EARS be the judge.