Currently using a V5i on my setup and using a headphones like the DT 990 (250 ohm ver.) and sounds pretty good over stock.
I do like the Sparkos Labs SS3602 on it instead but you will lose portability since you need to take it out of the case to work.
XDuoo, can you make a modified case that has increased height to fit weird opamps like that? Would buy if that were the case. (I don’t mind the case being chonky)