Advice Needed for office relocation

The Linksys router has four ports - I'm not sure why you need the 5 port switch...

Charter -> Edgewater 4550 <- Bridge -> Linksys E4200 -> Linksys EZXS55W -> Desktop
I'm not sure that you really want a bridge, but you have to make sure the two devices are different addresses (both cannot be the default if the default is 192.168.0.1 or 192.168.1.1)

The software lives on the Desktop acting as a server - right?
The laptops connect to the 4200 and go through the switch to the Desktop server - there's no Internet required for the software?

An easy test would be to connect the Desktop directly to a port on the 4200 (you'd have to undo the firewall change to test). Most routers have port forwarding and that might be something to look into (if you can boot up the old Linksys E2000 router, you could compare the configuration to your new router. Time makes us forget the little changes)

Another easy test would be to connect the old Linksys E2000 in place of the new 4200 - basically mimicking the old network with a new ISP.

Easy, but can be frustrating. You might have to restart the Edgewater device and that's not fun when your phone system is on the device.

If you decide to test the old configuration (edgewater -> 2000 -> desktop) do it off hours and have Charter's number handy and a cell phone. These are precautions, hopefully you won't have any issues testing - but.....)

Without details (port #s, software affected, network addresses, router configuration) I won't be much help, but I thought I drop in and offer some suggestions for you to test.

You can also test your ports for security, there are many sites out there that will help you do that. There are also windows programs you can download to test what ports are showing as active, stealth, or blocked.

Sure, you can try using the same SSID so that you don't need to configure anything new on a device (laptop that is carried around)
--> The problem with range extenders is you lose 1/2 of the bandwidth

-- OR --

Configure a new access point with a new SSID on the E2000
--> If you have your laptop or tablet to automatically connect, it should connect to the SSID with the strongest signal.

You'll also have to configure the E2000 with a new subnet (ie. 192.168.2.1)

Charter -> Edgewater 4550 <- Bridge -> Linksys E4200 -> Linksys EZXS55W -> Desktop
+ Charter -> Edgewater 4550 <- Bridge -> Linksys E4200 <- Linksys E2000

If you could post the IP addresses for each device, something like this, it would be helpful.
192.168.0.1 - Edgewater 4550 (guessing)
192.168.1.1 - Linksys E4200 (guessing)
192.168.2.1 - Linksys E2000 (proposed)