Why did you add a second "router" (i.e. the E2500)? You describe only a PC and NAS connected to it, which I assume are both wired-connected to the E2500. Doesn't sound like you need any of the wireless capabilities of the E2500.
What you really should have done is get a "switch", not a router, to satisfy your needs to connect that PC and NAS. A switch has none of the firewall and security features that a router has. It's simply a "port-multiplier" which has one upstream connection port (say to a wired port on your primary Comcast gateway, i.e. modem + router combined), same as your E2500 is currently connected through its WAN port to your Comast router. The switch also has an additional number of downstream ports, to allow devices in its physical vicinity to be wired-connected, same as your router did. So to the downstream wired devices currently connected to your E2500 the "switch" device looks identical, and provides the identical access to the Internet.
But the switch will provide unblocked access to all other devices on the primary LAN hosted by itself as well as by the Comcast router. And it will also provide unblocked access to all downstream devices, to any upstream device (like your first computer). Everything connected through the switch appears identical to how it would look if connected directly to the primary router, and access between ALL devices is now possible and unrestricted by firewalls and security (since there's no second router involved).
The net effect is to provide wired connection of all the downstream devices to the primary router, as if they each had their own individual wired connection to the primary router. But they don't each have their own wired connection obviously, they're simply sharing the one upstream connection from switch to router, splitting the bandwidth (of that one upstream connection) as needed whenever they need to.
So, using a simple inexpensive reliable "gigabit switch" such as the
Netgear GS105 instead of your E2500, you would connect the same cable between the Comcast router and your current E2500 to one of the ports on the GS105. Then you'd connect your second PC and the NAS to two more ports on the GS105. Bingo, presto, the second PC and NAS are now part of the primary Comcast LAN's attached devices, exactly as if they had been connected directly to one of the wired ports on the Comcast box.
That's my suggestion. A home LAN with two or more routers isn't "friendly" because of the firewall and security issues (which can be disabled, but really shouldn't come into play at all). You simply want the "port-multiplying" function of a "switch" at the remote room locations around your house, to provide additional wired Internet connectivity (say to smart TV's and players) where you have only one ethernet cable run to that room.
The multiplexing effect of a switch provides no greater than the upstream maximum speed to any of its downstream connected devices, but as long as they're not all working at the same time you might as well have full speed to each downstream device. Otherwise, they will "share" the upstream bandwidth.
NOTE: if you actually do need wireless capability in the neighborhood vicinity of that GS105 switch (which itself only has wired capability) because the wireless range of your primary Comcast WiFi router doesn't reach far enough with sufficient connection quality and speed, you can add an inexpensive "wireless access point (WAP)". This is another form of "switch" which includes both wired and wireless capability (like a WiFi router). The wireless network radiating around the WAP is a SECOND wireless network in your house, and is facilitated by the wired connection between the WAP and the primary router.
If you need this (i.e. remote WiFi to areas of the house where the primary WiFi network can't get to), we can talk more about it. But the nice thing about a WAP is that it provides secure access to its own second WiFi network (same as your primary router provides secure wireless access to it), while at the same time all devices connected to the WAP either via wired or wireless are actually hosted by the primary router. They all still appear as "wired connected devices" to the primary router and have full access to all devices on the one primary router LAN, no matter whether they are connected wired or wireless to the WAP.
