Hi @in1voice
I had a very similar setup to yours. It was:
Netgear Orbi Satellite => ISOCAT7 => Cat7u => Innuos Zenith 3
I was in communication with May Park at SOtM at the time and this was the configuration she advised. I did also ask her where a decent audiophile switch should go in this chain and she advised it go before the ISOCAT7. So this seems to agree with your dealer's advice.
There's a big "however" here.
For me, this setup didn't really improve my SQ. It was brittle, digital, sibilant. Not at all what I was aiming for. In desperation I bought an Uptone EtherRegen (not dissimilar to your Paul Pang perhaps), and put it before the ISOCAT. But no improvement was observed.
I was about to sell the ER on again, when I tried taking the ISOCAT out of the setup, and BOOM: magic. The harshness disappeared. It was day and night. It appeared that the ISOCAT was undoing the good work of the ER.
I have since significantly upgraded my ER "ecosytem" (see below), each improvement bringing more.
The ISOCAT was sold on.
Current setup:
Orbi => Startech FMC with Finisar FTLX1471D3BTL => Phoenix Contact fiber cable => EtherRegen with Plixir BDC Elite LPS; and AfterDark King clock with LPS and Oyaide BNC cable => Cat7u => Zenith