AN Niobium versus Tantalum resistors?

Just went through some resistor comparisons between choices for Khozmo and Hattor preamps and my SMc buffer.  I have not tried the AN Niobium resistors.

In my Hattor preamps, I tried the Takman metal film and liked the sound but I actually liked the Amtrans AMRG Carbon Film Resistors better.  They just sound so musical in the Hattor Big preamp compared to the Takman REY metal film resistors in my Khozmo passive, which also sound good but more precise.  I have not tried Takman REX carbon resistors.

 In my SMc buffer/preamp, the volume control (that I removed from the circuit) used AN Tantalum resistors, which were very musical with a smooth groove.  I replaced the VC in the circuit with two Audio Note Silver Tantalum non-magnetic 2W resistors .  Those AN silver resistors sound very nice having body, resolution, and musicality.   In summary, my favorites (of what I have heard) for preamp use are the Amtrans AMRG Carbon Film Resistors and the Audio Note Silver Tantalum non-magnetic 2W resistors.

In my Khozmo passive, the shunt resistors are the Takman REY metal film resistors and the single fixed series resistor in each channel is the Vishay z foil naked resistor.  As described by PW,

"their utter transparency can prove too ruthless and become overtly clinical" 

This becomes a personal choice but they are revealing for sure.

Regarding the Amtrans AMRG resistors in my Hattor BIG preamp, I believe they offer a couple of levels of resistors - mine are the black carbon film resistors.  All I can say is that they sound very nice with a good balance of detail and musicality.  The big Audio Note Silver Tantalum non-magnetic 2W resistors I used to replace the Shallco VC in my buffer also sound very good and seem to be well-balanced.

Based on the HiFicollective website, the AN Silver Tantalum resistors are more than twice as expensive as the AN Niobium resistors.  In the audiophile world, the price of two of them to use as series resistors in a shunt type VC should not break the bank.  They actually do sound great in my buffer - a touch of body and glow.  My Khozmo passive that uses Takman REY metal film with two zfoils in the series positions sounds very "clean" in comparison (when used with the buffer).  Maybe I should let those break in a bit more before judging, however, the Amtrans AMRG resistors in my Hattor passive sound just right when used with the buffer.  The only way to figure out what you like in a particular application would be to actually try them.

I replaced the VC on my preamp with two AN Silver Tantalum resistors, turning it into a buffer.  The AN silver tants are huge in size and while maybe not exactly neutral they sure are musically enjoyable, IMO.  I have an outboard passive VC with Takman metal film shunt resistors and Vishay z-foil series resistors and it is comparably a little hard (but neutral) sounding compared to my other outboard VC that uses Amtrans AMRG Carbon Film Resistors, which I find to be a good combination of musical and detailed.  I doubt I would gain anything by replacing the AN silver tants with AN Niobium, but it would be easy to do.