What a great review Amir, thanks for bringing this to us and providing the chance to enjoy our music even more. Also enjoyed reading your Technical Background
(1) and your great achievements.
I'm looking to buy a Bluetooth DAC/AMP with 10 band eq. that has enough juice to power my Drop HE4XX (which as you know was designed based on HE400i). I'm using my Galaxy Note 9 as the music player on the go.
Reading the review of Qudelix-5k, which was done using Bluetooth makes it difficult to compare it against ES100
(2) which was reviewed as a USB DAC as you mentioned yourself: "Testing Bluetooth devices is challenging since my analyzer cannot control them directly. Fortunately the ES100 also acts as a USB DAC on Windows". "All the tests including this dashboard were conducted by using the ES100 on Windows. With phones depending on the software you use and especially with Bluetooth, you may get degraded performance".
So, In your understanding and considering my setup, is there a benefit in getting the 5k instead of ES100? Would you pls elaborate ?