Devialet with waterfall niagara part of surround set

[ogs]

I don't think so. The goal of passtru in the Devialet is using a fixed gain so the volume of mch can be controlled by the Marantz in a consistent way. Levelling is already taking place in the Marantz so an additional step in the Devialet does no harm.
The Pro or Core Infinity version is primarily a sound quality upgrade, but RAAT is running on the CI for example. The CI is actually a Linux computer so it might be easier for Devialet to include future protocols and apps.