As for preamp I tried it with my speakers. It´s coloured but that was a positive for me. I do love what it does for my speakers since they can be harsh and I am in an all but perfect room. In many ways that is where the Head One shines the most for my setup.
The only thing that worries me being a cheap bastard is that I am running down the tubes so not running it as often as I would want to :)