Aries Cerat Helena or Mola Mola Tambaqui?

Hello - I have not listened to either DAC, but from an engineering standpoint, they are quite different. I think the answer may be in what your musical source is.
The Aries Helene uses 2 banks of Analog Devices AD1865 NK chips which can process up to 18-bit/96KHz. If your musical source is 16/44.1 CD then you are fine, but if you feed the Helene a high-rez 24 or 32-bit file, you'd have to dither that signal down to 18 bits or the DAC will truncate it down to 18 bits. I'm certain of this because my DAC uses the same chip.

The Mola Mola Tambaqui is a more modern design. The description seems to indicate that it can accept up to 24/192 via the USB input and 32/384 via the other inputs. It also will upsample all inputs to 32/3.125MHz. No truncating in this design.
Again, I haven't had the opportunity to listen to either one.   I'm not saying that your decision should be based only on the bit-rate you're trying to play, but it may matter, especially if you have a lot of higher bit-rate recordings.  I'm very interested in both designs, and I'd like to hear both.

What is your musical source?
Dave

I highly doubt if you’re going to run into many people (if any) who have compared these 2 dacs side by side. Personally, I would never buy a very expensive product without audition.  If I were you, I would go with something you can hear first. You may not even like the MM, which will solve your problem, but if you do, I would buy it. You can beat yourself up forever over whether you should have bought something else, but what good does that do? The MM is a very highly reviewed product, which I assume will give it decent resale should you decide to sell later. Plus you will have the peace of mind of knowing you made an intelligent decision by purchasing something you auditioned and loved. At least that’s what I think. Be well and be thankful you are fortunate enough to be able to own products at this level.

Just one more thing that may or may not matter.  I checked out the Helene on YouTube and it looks to be huge.  OK if you have the room and the back for it, but size and weight may be a factor in your decision.