To use or not to use preamp it depends from a system and amplifier topology.
I use SET 300B amplifier. And in this topology the short signal path is important.
My amp is integrated and it is a good solution for low power SET amplifiers.
I also have an external phono stage for vinyl source.
Both phono stage and DAC are connected to input of my integrated SET.
If someone use more powerful amplifiers (especially mono-blocks) with more sophisticated circuit and long signal path it is more reason to use preamp.
I use SET 300B amplifier. And in this topology the short signal path is important.
My amp is integrated and it is a good solution for low power SET amplifiers.
I also have an external phono stage for vinyl source.
Both phono stage and DAC are connected to input of my integrated SET.
If someone use more powerful amplifiers (especially mono-blocks) with more sophisticated circuit and long signal path it is more reason to use preamp.