@melm First off, as I mentioned previously reverse engineering required to determine quality of these clocks and power supplies, manufacturers rightly don't advertise their schematics and all part numbers.
As for usb vs I2S I've never stated all I2S implementations will beat all usb implementations, my previous experience with SU 6 and 005 being inferior to ubs proves this out. Golden Sound replicates ASR in that measurements tell all. I presume all 005 owners understand the fallacy of this what with it's poor performance over at ASR. More proof of this folly is my experience with Okto Stereo dac which at one point was SNR champ at ASR, jitter right up there as well. So, Okto vs 005 which measures poorly. Sold the Okto, kept the 005, amazing how a dac with lousy SNR was more highly resolving than top rated Okto. My point is one should pick the Singxer SU6 over the Gaia if measurements are your final arbiter for equipment purchases. I've had both in house, Gaia wins on build quality, design and sound quality. As for the Audio GD, I can only speculate as to it's performance, I chose the Gaia, happy with the purchase, especially with the Tubulus cable.
@catastrofe I understand the theoretically inferiority of external clocks via I2S interface. Well usb is also a very flawed interface, never designed for the purpose it's used for in dacs. Think about all the complexity of usb boards within dacs, lots of technology required to clean up this flawed interface. Back to I2S, well Gaia external clock beats out 006 internal clock, and not by just a bit, so much for theoreticals. Still, I'd advise sticking to 1/2 M or less for I2S cables.
Bottom line, I agree we should be concerned with design, parts, build quality, and measurements. After decades spent in audio, I treat measurements as perhaps the least important aspect for end users. Measurements are of critical importance for designers/engineers, not so much for us. Musetec, in their own statements admits their final designs based on listening vs measurements. I presume many other manufacturers do exactly the same.