Power supply to modem make a difference?

No. How could it make a sonic impact?

I would think in the same way it makes a difference for any other digital component such as a streamer or a DAC. 

Mine powered by LPS, more about not contaminating dedicated audio circuit with SMPS. This alone is good enough reason for me. Also, Broadcom chips reportedly and measurably best for modems, don't know if that still holds true in every case.

The issue IMHO isn’t noise via network but noise via the AC line, and potential for surges coming in from the cable line unless it’s fiber already.

For power supply issues I use iFi supplies like these. 

For surges I have one of these outside and then use Ethernet to fiber adapters to put a 1 meter air gap between the cable modem and my router.  I live in a lightning prone area where lightning did enter several neighbors homes the first year I was here, so I'm more nervous than most.

It depends on the quality of your streamer. Good quality streamers isolate the signal from the modem/router or extender. Cheap ones do not.