With regard to the upgrade issues you asked about, I would recommend the Phoenix USB and an Ethernet filter like the ENO from Network Acoustics. Their effects are additive. If I had to choose between the two, I'd give the nod to the Phoenix, but a demo in your own system could help you decide for sure. After I already had the Phoenix and ENO filter in my system, I noticed some improvement from going to an English Electric 8Switch to replace a basic Netgear switch in my Ethernet set-up. I have not upgraded my cable modem or router (or their power supplies) so I can't estimate how much of an improvement those changes might make.
Good luck with your decisions.

