Instead of buying a LPS for my Verizon router, I hooked up a spare Brick Wall power strip with RFI/EMI filtering. There was a noticeably lower noise-floor ( it is a power conditioner) and all RFI was filtered out. I confirmed this using my tester. I have no way to test EMI, but the signal is so clean now.
I agree with cleaning power at the entry-point to the system.