I have no idea what this sounds like and as there are no internal pictures to what standard the output Valve section is . Bitstream DAC's were noted for being smooth so perhaps not the best candidate for a Valve output stage as it may make this just too smooth and mellow . All that aside this is an interesting lot and if it was under £200 then reasonable value as well .
https://www.ebay.co.uk/itm/Mission-DAC5-Digital-to-Analog-Converter-with-Valve-Output/283642430862?hash=item420a68058e:g:AYQAAOSwTaFdRzOz
https://www.ebay.co.uk/itm/Mission-DAC5-Digital-to-Analog-Converter-with-Valve-Output/283642430862?hash=item420a68058e:g:AYQAAOSwTaFdRzOz