You want a wishlist for Dx300 ? Here
1/ Higher precision tolerances electrical components such as Capacitors and Resistors. Ofcourse also Audio-Grade components for Analog sections
*dont be mistaken, Dx200 is already with next to the highest quality available for electrical components, but there are better available as always*
2/ Better Battery performances (technicality, such as noises, AH, capacity)
3/ Quick charge
4/ 512Gb of internal memory
5/ SD card that is PCIE compatible and MicroSD slot.
880Mb/S
https://www.anandtech.com/show/12487/western-digital-displays-sd-card-with-pcie-interface
6/ Choices of DAC from Ibasso Engineers
7/ Better Clock precision’s components (there are always better Clocks)
8/ Silver traces Printed circuitboard (for ultimate conductivity)
9/ Silver Pins, goldplating interconect connectors for amp modules (for ultimate conductivity)
10/ High Grade Silver content Solder (for better audio performances)
11/ Faster CPU (not a priority)
12/ better cooling design (such as piped cooling for essentials chips Xmos and DAC)
13/ Easier to access and replace battery pack
14/ Maybe some possibility to open for further features such as AptX-HD and LDAC Bluetooth (not a priority)
Feel free to add in