remarkable low noise, your SH_SA44 looks much better than the SSA3075X-R.
Well, the SA44 has a very different mixing scheme, so it is hard to beat at lower frequencies and narrow spans. In general, it has quite some limitations, but whith the right settings it can outperform most of the "big boys" in certain situations.
Does its software exist for linux or is it windows only?
There is at least a Spike version for 64-bit Ubuntu.
Here my screenshots, 100 MHz signal originates from SDG6052X.
My signal source has been a SDG6052X as well. For the following screenshots this wasn't even necessary, as the SA44 happens to produce a strong spur at exactly 100 MHz

The attached screenshots show the noise floor around 100 MHz with and without preamplifier.
SH_SA44_Noise_100MHz_PA-on
SH_SA44_Noise_100MHz_PA-off