I have a buffer with the 12/6 volt switch, it's very versatile. The tube options for it, are as versatile as you can get.
And every tube it runs is dead quite.
I haven't ever needed gain. And I have used it ahead of SS and tube amps without any issues. Driving some 4 ohms speakers with 88 db sensitivity rating.
The 12/6 volt switch is awesome.!
(Imho, the VGP would change the sonics and make it even better, in some setups. You can't go wrong, if you can have/have not gain, just another great option. )