Best tube preamplifier for under $15k

Herron Audio VTSP-360.

PLEASE LISTEN: 
I can guarantee you that the MicroZOTL pre 
beats out my Pass XP30, 20, 22, and, my Conrad Johnson GAT And all other pres I’d thought we’re under $5000 giant killers. In my MicroZOTL I’m running great tubes. The 6SN7’s which to me have the sound I like. In addition the volume attenuation step in Tenuate or on the MicroZOTL is excellent and on par with both the Conrad Johnson and the pass labs although possibly not as smooth as Pass 

Mcintosh C1100, its Mc's the top of line dual chassis, dual mono config, amazing quiet.

The most transparent preamp I have heard is Concert Fidelity CF-080LSX2.  Can find on used market for great prices.

Here is an old review:
http://v2.stereotimes.com/post/the-concert-fidelity-cf080lsx2-hybrid-preamplifier

There is no best anything.