Let's sort through this. You currently have the following equipment:
1. ARRIS TG1682
2. ARRIS TM3402
3. Technicolor CGM4141
Are you still renting the TG1682 from Cox? If so, you're renting 2 routers from Cox: TG1682 and CGM4141.
Fundamentally, you need 3 devices: an Internet modem, a telephone modem and a WiFi router.
The TM3402 knocks out 2 required devices: Internet modem and telephone modem (technically, an eMTA). You NEED that.
You need 1 other device: a WiFi router. You currently have 2: TG1682 and CGM4141.
I'm not sure which is better...probably the CGM4141 because it's newer...so whichever you pick, goes in the closet. Return the other one. OR...this is just me...buy a better router with the ports you need and stop the fees. If you agree, return both routers: TG1682 and CGM4141.
Mouth is here...he can recommend a quality router...if you go that route.