There seems to be an echo in here.
Come back when you can reliably (at least 9/10 times) pass a properly controlled level matched blind comparison, and there might be something talk about.
I think Sabre and AKM IC's have different developing philosophies and market targets. As far as I know, brands like AKM or Burr Brown don't make D/A IC's aimed at mobile phones or DAP's, while Sabre or Circus Logic do.
AKM or Burr Brown develop and make D/A IC's aimed at the Hi Fi or professional market, while Sabre make a bit of everything.
My critisism with the Sabre based DO300 wasn't bad sound quality issues, in paper after being measured with the proper equipment, Sabre ICs measure highly well with very high numbers on SINAD, Signal to Noise ratio, dinamic range and the likes, outperforming top of the like IC's by AKM or Burr Brown, yet AKM and Burr Brown IC's when well implementes sound arguably and subjectively better, more pleasing to many people's ears.
I didn't move from the SMSL DO300 to the DO400 PRO straight on, I first got an AKM based SMSL DO300 EX, which features the same IC's as the DO400 PRO, but on a lesser build quality, simpler power supply and added a headphones output, something redundant to me.
As I prefered the sound of the lesser DO300 EX to the Sabre based DO300, I decided to move to the better built and better power supplies of the DO400 PRO. After some hours of breaking in, I loved the sound of the DO400 PRO.
I've had two Sabre based DAC's before, I don't remember the reference of my first Topping , I then got a D50, which for the money sounded extremely clean and dinamic (powered by an external linear power supply), but I found its sound tiring, uninspiring, boring, despite its high measurements.
That's when I moved to the DO300 and I find a more detailed sound next to the D50, but same tiring and "cold" sound. So I started looking for something aforddable but with and engaging and inviting sound, and that was the AKM based DO300 EX. The DO400 PRO just took its sound a step further. It's been on my set up since early July, a Marantz PM 6007 integrated amp, KEF'S Q550 speakers and Sony's UBP X-8OO M2 as a source, with "the" Chinese HDMI audio extractor so I can play SACD's and DSD files vía the DO400 PRO, as you see, nothing expensive or fancy, and I can tell you the DO400 PRO stays and Will be there for a long time.
I had never been Happy with none of the Sabre based DAC's I owned before.