The email I got for this just now says this, so hopefully they fixed the noise. I don't see the verbage about the noise floor on the website.
"The Seed3 sports a new audio codec with crystal clear audio. Up to 32-bit, 192kHz processing and an unbelievably low noise floor (-120 db)."
Side-chaining is when a signal output controls a parameter of another effect. So in Feral's example the autowah and compressor would have to have a separate input for the sidechain trigger that routes to one of those particular parameters, which in the case of the autowah would be the split dry...
Sorry, you are right. Solid state amps tend to use tanks with a higher input impedance. I don't see it specified in the schematic but from what I see online, other ss ampegs use something like a 4FB3A1C