Hopefully I'll be a proud owner of the Vali in a couple of hours! I had a question though while I impatiently wait: do you think it's a mistake buying only the Vali and not it's best friend the Modi as well? The Modi was out of stock where I bought it (dealer Netherlands). Do you think it will be enjoyable on it's own (used with a Hifiman HE-400 and soon a modded T50RP)? I never had an amplifier before, so I figured it would be an improvement either way
Consider an Audio Quest Dragonfly. If budget is a concern, go with version 1, they are basically being given away, even new. Just be sure to get the dragon tail adaptor, its easily worth the 16 bucks and also factor in cost of a cable that will send the headphone signal in stereo to the Vali. 1/8 to stereo cables are everywhere, just don't pay too much! I recommend Blue Jeans cable "MSA-1" at 30 but some head-fief's might say that is even too much.
I have such a setup with the dragonfly 1.2 and it works quite well. As a bonus I can pull the Dragonfly out and take it with me to use with portable headphones on the go.