I would like to add one more thing about the processor: I think one of the reasons why iBasso (and also A&K on SP2000) is still using the older (2015) RK SoC is DSD512. It was a question asked, why FiiO M15 is not supporting DSD512, and James from FiiO said that the I2S bus of the SoC is not supporting it, and it is a much stronger controller from Samsung. I don't know if there is any other DAP that supports DSD512 _and_ Android, but chances are that, switching to a new processor/SoC could mean losing the DSD512 capability.
(An open question for me is how Lurker's firmware works over the XMOS chip (pure USB access mode) - how it is connected to the rest of the system that this mode of operation is possible.)
But anyway... People complain a lot about things, about the size and features and heat and processor etc. etc. Unfortunately there is nothing that thicks all the boxes - all these parameters play against each other. And a new processor would most probably mean losing the DSD512 feature, which is a "one of its kind" feature for iBasso TOTL DAPs. The SoCs are not built really for such niche products, but rather for other mobile platforms like mobile phones, for which DSD512 is not an important point. DSD512 over USB did not sound any different for me on M15, but on DX220 the difference was quite obvious (and I had it confirmed with my wife - which she did not like, as she did not like hearing that much of details).
So...it is all about the preference, and today we are just spoiled with all those amazing products in the market.