Frankpiet,
Glad to hear that you're happy with your Boulder gear. I am sure there are synergies when listening to an all Boulder amp/pre-amp combination. Are you using XLR connections between your sources and the pre-amp?
Looking back at it I think the fact that my Linn CD12 and Unidisk source gear sound their best via RCA outputs (vs XLR), and the fact that the Boulder pre's are an all XLR design, was the reason that I prefered the VTL and the darTZeel pre's over the Boulder.
In any case, I stand by my comments, but acknowledge readily that there are many paths to audio nirvana in this hobby and in many cases what that means comes down to individual tastes and how individual components match with each other.
Have never heard the Ayre gear so can't offer a comparison versus the darTZeel pre-amp, all I can say is that I'm extremely pleased with my dart pre and amp. Further, I don't see any dart gear for sale on the GON which is a further indication that those who have it at this point are happy. Perhaps that may change over time.