Router improvements

I have a CGM4140COM modem / router I am leasing from Comcast. I think I would like to upgrade to one that provides QoS capabilities ( and any other advantages to assist with optimizing bandwidth across multiple devices). Looking for recommendations.

One thing that leaves me puzzled is i have a landline connected to my exsiting router, and this does not seem to be a standard option with 3rd party routers.

Thanks