I realise there are two conversions, and honestly I would likely want to go all digital myself. But the thing in question was if he'd hear a difference! Someone on here did a teardown of their 8351b (
https://www.audiosciencereview.com/forum/index.php?threads/i-disassembled-my-genelec-8351b.14874/) which is a top of the line model, and found Genelec was using AK4621EF in that model. Specs are here:
https://www.akm.com/global/en/products/audio/audio-codec/ak4621ef/
The AD-DA specs are well-matched and are fine. If we assume that the other speakers are going to use similar chips, we are good for ~-100 dB. CD transparency (which is already well beyond the limits of human hearing in the context of listening to virtually all music) is <99 dB, so hopefully their circuit was implemented to get the most out of the chip spec.
Good speakers like Genelec with good radiation and frequency domain characteristics, low distortion etc. with "crappy" internal electronics (i.e. worse than the DAC SINAD numbers we are used to here) will always be preferred in terms of overall objective performance/fidelity versus top performing electronics with inferior speaker systems, because the transducer is the bottleneck and has orders of magnitude higher distortions than the electronics. Inferior electronics+good speakers will sound virtually identical to superior electronics+good speakers if they are within the realm of transparency in normal conditions. If Genelec were to put top of the line chips in their speakers and implement them well the costs would go up significantly, and have no real audible benefit. Going all digital can definitely simplify things and ensure good integrity of the signal and give piece of mind, work better with professional workflows, or could provide a more elegant option with less devices in the chain