Adding Valves to a setup - Music Fidelity X-Tube

This concept of a ‘Tube Buffer’ goes back decades, but has been reincarnated and recently released by Music Fedelity. Has anyone bought one or tried one, interested in the results. I really like my EAR valve Phone Pre-amp, so am intrigued how this will sound in a digital pathway https://www.musicalfidelity.com/products/x-tube