I had mentioned waiting to hear about the Mk3 upgrade from Innuos. I grew impatient so just purchased a Mk3 and then sold the Mk2. I mentioned this because the main difference between the two is the power supply. It was a significant upgrade so that makes me think the power supply plays a big part in a server’s sound quality. So I’d be inclined to go with S30 + S60 over S40 alone. But best to confirm with Antipodes.
Where the S40 would have the edge might be if you wanted to ditch the Nucleus. Low noise matters a lot on the server side too - as do power supplies. Since you aren’t doing DSP, the S30 might be powerful enough to run Roon core. A little extra horsepower there might help though especially if you have a large music library.
I have found Mark Cole of Antipodes to be an awesome resource. That’s another advantage one gets with Antipodes over the other two brands you mentioned. Mark is helpful both before and after the sale, so definitely run it by him.
Have you heard of PGGB yet? This does offline upsampling using a similar philosophy to MScaler. Hearing this was a big reason I moved to Antipodes as it gave me a few different playback options. I think you might be stunned by the improvement PGGB brings providing you run your server directly into your DAVE. More here:
https://www.remastero.com/
I actually sold my MScaler to help fund the purchase of my K30. The lift from doing that was worth every penny and then some. When streaming I will use HQPlayer to scale. While it alone doesn’t bring as great a lift as MScaler, the lift from a better music server left me not missing MScaler at all. Just some food for thought.