I think the question should be: is there any technical advantage of using a retail product as an end point? HiFiBerry, Allo et al are businesses too.
We both use S/PDIF and some would argue that this interface is archaic. Yet when paired with a quality DAC performance is on par with the best USB streamers.
So, does the Pro-Ject Stream Box S2 Ultra, for example, perform better than the AURALiC Aries, AURALiC Aries Mini, Metrum Ambre, Metrum Baby Ambre, HiFiBerry Digi+ Pro, Allo DigiOne, Allo DigiOne Signature etc.?
The only one way to find out is with measurement or auditioning–not so easy–but I would hazard a guess that the differences between each are not going to be earth shattering when pairing with a good DAC. @RBM sums things up nicely in this post:
Most of the streamers listed use the RPi (or RPi Compute Module) and all designers seem to understand the shortcomings of these computers and address them–in their own way–using their unique designs. That usually means improvements to timing, noise and power supply. Since the DAC doesn’t control the clock of an S/PDIF connection, I think a lot of the claims some manufacturers make about their device is moot because the age old issues of jitter and noise are often addressed by the DACs input circuits, e.g. clock recovery, RF filtering and reference power supplies.
I’d like to try the Baby Ambre, but I think it is hard to justify the price for a potentially small gain. So my money (for now) will go toward new speakers.