Thanks for the very interesting and tempting recs of the KA13 and K11 for the Yinman 600s. Have you tested either or both of these against the VE Megatron? My humble ears are very satisfied with the Megatron for the Yinmans, even though it lists a PO of "only" 300mW@32 Ohms (2.5mm & 4.4mm balanced). (Several members of this forum,
@JAnonymous5150 and others, have had the opinion that the actual output of the Megatron is much higher.) I tried the Monolith by Monoprice Liquid Spark, with a listed 1.3 watts at 50 0hms on a deal from Amazon, but could not hear a difference in dynamics between it and the Megatron. Frankly I preferred the Megatron, because the Spark had a warm coloration that was pleasant, but not as punchy and clear as the Megatron, so I sent the Spark back to Amazon.
I may try one of your Fiio recs from Amazon. Can you hear the difference betwen them with the Yinmans? It is interesting that a recent Megatron reviewer here heard no discernable difference between the Megatron and the Fiio K7, which I had also been considering.
https://www.head-fi.org/showcase/venture-electronics-megatron.26010/reviews However, he only tested these Headphones: HD600, R70x, MDR-Z7, none of which is as hard to drive as the Yinmans.
By the way, I realize this may be a polarizing recommendation, but I love FXSound with the Yinmans. It is "Free software to boost sound quality, volume, and bass. Including an equalizer, effects, and presets for customized audio." To my humble ears, this brings the Yinmans, and my other buds, massively and vibrantly to life. My rec to all is to check it out if you haven't already.
https://www.fxsound.com/