I bought it directly from Germany, somewhere around $80. Agree with you and originally had it before the switches. Had an Aha moment when sticking it right in front of the server. The system seemed suddenly 2-3 db louder and more resolving. Given the effect I think it was more likely some ground level noise than RFI but not sure
Galvanic isolation revisited.
Even using two switches and an Etherregen between router and server, inserting a EMO Isolator between Etherregen’s B side ethernet link to the server in my case brings substantial benefits. Likewise galvanic isolation between server and DAC on the USB link (I use an Intona Isolator) is indispensible. Given the Etherregen’s moat and modern DAC’s noise reduction circuitry I find this surprising. But obviously RMI/EFI and ground level noise intrusion in densely populated areas is difficult to fight.