I am using V40, SQ is much an improvement over my earlier DAP AK100II. LG sound much more layered with better separation, do you think it worth investing $400 for this DAP, or used continue using LG
I would say it depends on your usage. On the go with more easy to drive iems or headphones I don't think you will hear a difference. If you listen at home and analyses every note in the music probably yes.
Your ier-z1r needs some juice, maybe that would benefit with a proper dap?