FWIW - this is way ahead of the Nac272 solution in terms of SQ. I sold off my Nac272 more than a year ago, replacing it with a Naim Dac, Nac72. A HicapDR and a UQ2 I happened to have at home anyway. Speakers - Trusty old Kudos X2s.
Naim DAC to the left stack and TTPSU to the right would be my suggestion. UQ2 could go to the left too as you’re not using its power amp section (I assume).
My take would be to place them in the way that looks best to your eyes, or if your rack shelving has different dimensions then place them in whatever way best ‘fits’ your hi-fi gear.
The one concession I would personally make to stacking order would be Rega RP6 on the top shelf. However, I am sure that most on this forum wouldn’t agree with me (apart from Rega on the top shelf that is).