I will chime in here regarding Sony Signature series. Though, I have not heard the wm1A, but I can share what I found with WM1Z and TA-ZH1ES and Z1R
If you hear the Walkman connecting into ZH1ES out of Z1R Balanced (4.4mm) with upgraded cables. Yes, the sound quality seems to have suffered in comparison to straight out listening to WM1Z (4.4mm), and flame me all you want, but that is because the stock Digital out Cables that comes inside the ZH1ES is not good enough. The same as Pha-3 and it stock WM cables.
I tried this way with upgraded WM digital cables NWH10, and it was much better. However, I lost the function to charge the Walkman while connected. Then I turned around to use the Zx2 Dock cradle and Upgraded USB cables. The TA-ZH1ES will show it superiorities over the WM1Z/A, period.
"Why don't Sony offer new Cradle Dock for WM1Z like ZX2 ?"
I have no doubts that people can tell right away the differences between WM1Z/A. However, the WM1Z is capable of so much more if you do an upgrade to it internal wires. Instead of using Kimber wires, go with some other upgraded materials and witness what WM1Z can potentially bring to the table.
All in all, I am just saying that Sony signature series are worthy of being high-end products. It may not be super expensive, or super high-end, but it quality is good enough that even upgrading the cables all around it will bring observable improvements. Therefore, if you love Sony products, and have any doubts, these products are capable of so much more with upgraded cables all around (USB cables, headphones cables, powercord)
**Sony** if you are reading this, please, in the future, include good stock digital USB WM cables to your DAC/AMP. Just because the performances are real, and the Popularity to just specially make these cables are not high, and people generally can not find good enough cables for your WM port. It may be the little thing in the chains but will obstruct your sale figures.