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Headphoneus Supremus
All you would need to know is that AK4497 is the Flagship from AKM with the highest dynamic range in the line up. Sabres also has newer flagship which is currently the king of Dynamic range for DAC chip in the industry. It has a whooping 140Db dynamic range if run mono, and about 128 or so if run in stereo, and it is the ES9038Pro
Then, next up, it is not the matters about the DAC alone, which is equally important is the implementations, the supporting components, the power supplied....etc. However, DAC itself is an easier term for marketing the players
Different people prefer different DAC as they believe different DAC carry different sound signature, which is correct to a degree
I actually ignored the new measured specs. In my mind, I have no idea how I would be able the enjoy 140 dB of dynamic range without literally killing myself. Like you say, these are just "bigger and faster" specs and the implementation matters at the end of the day. My comment about "big upgrade" was purely in context of RWA. I fully trust that Vinnie Rossi doesn't upgrade his DAC chips just because they measure better and for pure marketing purposes. When AK announces new DAC chips, my reaction is "so what?". But when RWA announces the same, my reaction is "whoa!".
Having said all that, I would not recommend anyone buying the SP1000 purely on the basis that the DAC chips are AK4497. I also think AK can step up their game with user selectable filters and NOS mode since RWA offers that on the new LIO DAC 2.0 module that is priced similarly.