That's a good point. This is really more of a DAC+preamp comparison than a DAC comparison. The F1 shouldn't be hard to drive though (I'm only guessing here based on the fact that it's SS with low output power).
As long as it sounds good, who cares about the sampling rate? Are you saying that the 192kHz mode on the Stello should not be used in this comparison simply because the Lavry is not capable of it?
Ideally, both units would be using the settings that give the best sound. While the crystal mode is not necessarily the one that sounds best to humanflyz, at least it is recommended by the manufacturer.