Ayre KX-R Pre

Has anyone had the opportunity to do a more extensive comparison of the Ayre KX-R preamp to the other available preamplifiers (SLP-05, ARC Ref 3, VTL 7.5, P8, ML32 6010D)? I know that there is a "Wow" factor in the design, plus blacker backgrounds and more detail, but how much real bang for the buck does this unit offer sonically over other options that can be had in the $5-10 k range new or used?