They are .5W because of space issues, I was not able to go higher. I use standard Niobium, which are higher resolution and fuller sounding than Z-Foils, as a comparison. They are the highest resolution resistor I have tried so far and the tone curve feels natural and nothing weird, no rhodium/silver tilt etc. Just a great improvement to the Takman sound I was getting before. You lose a touch of "exciting" metallic felt-texture, but its worth it for the naturalness of the music. And that part is totally subjective anyway.
Have not tried tants but read many reviews of them before deciding. There’s a website which said the Niobiums are "musically" on a higher level than silver tants, although the silver tants may give some improvement in certain areas.
I want to try the silver Niobium this summer. At first I thought I needed them because these began VERY warm and dark, even at 100+ hours. Then they shifted bright and brittle. They went back and forth until you get both warm and top end, but then they are sluggish. Thats when I removed them. But when I put them back, the next 150 hours cleaned and tightened up the sound and they are super solid now. Even bass-heavy techno music sounds as tight as metal resistors, but like a flood gate of music and transparency comes out.