I recently tried the Audio Note Niobium 1W resistors in my preamp. I put them in the signal path inputs, in place of TX 2575 (naked Vishay Z-foils). I'm a fan of the Z-foils, but using too many is too much of a good thing. Over time, I noticed the result was a little lean and hard sounding on some recordings.
The Niobiums have better tone color, maybe just a tad more depth, and cured the problem. In terms of transparency/presence and low noise, they didn't give up much, if anything, to the Z-foils. It was a worthwhile trade-off. I still have Vishays on the outputs. They pair well together.
Lots of good information in this thread - THANKS!