It seems on the ASR forums, there is a manual way to updated the firmware, opening the unit and using a USB SWD Adapter to directly program the STM32F103VE MCU. I've message SMSL Mandy over there to see if they can help as I recently bought a V1 M500 and whilst it sounds pretty decent, it seems...

Just thought I'd resurrect this thread,   I was using an E7 for a year or so for work duties since my work laptop had terrible on-board audio.   I then bought some DT770 250ohm headphones, and although the E7 flat out can just about drive them, you can't EQ the bass up or get elevated...