Which External Linear PSU Upgrade for my Router?

These are on higher price points, but will also deliver on a higher level of performance:

Farad Super3, around $550-700

Ferrum HYPSOS, around $1200-1400

The Ferrum option is very versatile as it allows you to customize the voltage should you want to use it with another component down the line. They also now make a dual output device as well so you can power two components that have the same voltage. 

In my system, I found the performance of the Ferrum Hypsos to be above that of the Farad, so I became a Ferrum dealer.

Lots of reviews of both online. 

@tsampa - I want to hear more about using a car battery for the power supply.  what cables did you use?  where did you put it?  is it possible to post photos on this forum?

One consideration that might mitigate the need for LPS on modems, routers, etc. would be to use a separate music server and streamer, with the server located in a separate room (often with the network equipment) and away from your main system.  Locate your streamer in your system room and connect the two through an optical cable.  Even if you do not use a server, connecting your streamer using an optical cable could do as much to reduce noise as using LPSs.  With a lot of this stuff, you need to try it for yourself, in your own system, to figure out what actually works best.

I've never not heard an improvement when using lps on streaming components, Presently using combo of Teradak, Uptone JS2 and JCAT ATX on every streaming component, same Teradak has been running two different Netgear routers, present XR1000 24/7 for well over four years without a single issue.

+1 For Ferrum Hypsos