Really enjoying my Vali after a couple weeks of continuous use with K601. No noise floor, no ringing, more power than I require. Have a Modi coming to see what that's like - always nice to have an additional point of reference, especially one designed to go with the amp.
I love the warm little classy box with it's impression of tube heaters - the biasing LEDs!
Today I noticed that horns can sound particularly excellent with the K601/Vali combo. Just the right lively, rich, blatty sound. I'm gathering jazz and classical trumpet recordings. Really fun.
Noise will be noticeable if you use sensitive cans or IEM's. Perhaps the K601 isn't sensitve enough to reveal the Vali's noise floor. Sensitivity is not an indicator of SQ, so enjoy your kit.