192 from usb/spdif to NOS dac to amp

That's what I think too, so if Audirvana sees the converter as being capable of 24/192, it will process at 24/192. At that point, the output of the converter sends data to the NOS Audio Note dac.
The dac cannot over sample anything and it has no way of telling that the data has already been up sampled before it arrived via the coax.
If this is correct, the finding the right converter would be next. I am thinking that this is where jitter would be something I need to understand a lot better,
Steve, is my thinking aimed in the right direction?

MattZ - absolutely, jitter is much more important to reduce than increasing the sample-rate, particularly when using a NOS DAC because there is typically no digital filtering.

Upsampling helps the most when the DAC is a Sigma-Delta and uses digital filtering. upsampling tries to mitigate the effects of poor digital filters.

Steve N.
Empirical Audio

What does sigma delta mean?

I have always understood that NOS dacs are less effected by jitter than upsampling dacs. Also my Audio Note transport has no jitter reduction at all. Audio Note does not feel that jitter is really a problem with there gear.
Alan

Matt, the difference between traditional converter and
sigma-delta is pretty much the same as the difference between
CD and SACD. Instead of creating many discrete voltage
levels, corresponding to input code, Sigma-Delta creates
bitstream of varying duty cycle that after filtering (taking
average) delivers voltage proportional to duty cycle. SACD
is exactly that but unfiltered yet. There are several
advantages of Sigma Delta the most important is moving
quantization noise to much higher frequencies outside of the
audioband. Quantization noise in normal people language
means simply "steps". Sigma Delta has only one
large step (being one-bit converter) but repeated at very
high frequency. Any residue of the steps has very high
inaudible frequency. For SACD it is 2.8MHz.