Esoteric need a pre-amp?

With K-01X Esoteric dropped the internal volume control feature that was formerly in K-01. While I don't need that feature, I do wish the K-01X had the ability to change between the selectable up-sampling and filter options via remote control. That would be useful.

The X series got upgrades but lost the volume control

You only need a (good) preamp if you want to hear all of the beauty the machine can unleash. If you don't want all of the magical midrange, go w/o the preamp.