'I take it from your answer that it was felt that the Phasure was "benefiting" from the Preamp. And that without the Preamp the Phasure would be rated lower'
No.
All DAC's benefited from the pre effect.
We would have liked to check all DAC's without the pre, but, since all experienced the effect what I think the most likely outcome would have been they all have maintained their relative position, but simply didn't sound as good.
Of course the Phasure may have been the best, or the Killer was a lot better than the Phasure instead of it being a personal preference, or the order may have been reversed, all sorts of things are possible. There is no way of knowing.
Also there is the issue of personal preference. There is obviously some kind of euphonics going on with the pre. To me its subtle and I couldn't get a grip on it, but some may simply not like it.
Thanks
Bill