Thanks for advanced details. Im seeking a smooth sound. Without sparkling highs but not mitigating the other strengths of TH900 (deep scene, punch and deep bas).
I definitely need to try BHA-1 since even BP26 is step ahead from Gustard H10 working with low impedance cans
Well, I think it's a great choice for your HE-560's if you go the balanced route. If you are looking at buying one with the TH900 in mind you may want to order it with the low-gain reduction mod in place depending on your preferred genres. But I would expect a brighter sound, especially if you find the H10 bright (try switching op-amps in that one - a good thread on that). Otherwise you may just have to EQ a bit to your liking.