Is there a simple procedure to use your own router instead of the X1 router / modem combo? I understand you need the X1 device for modem / telephone, but is there a way to disable it as a router and use your own?
You need to enable bridge mode on the 1682 so that you don't have an undesirable double NAT condition on your home network;
If you're wanting to use your own router anyway, why not just ditch the Comcast gateway and buy your own eMTA (voice) modem? A Netgear CM500V will set you back around $120, true, but that will pay for itself in a year since you won't be paying the $10-$11/mo rental fee.