I'm the same type of user as you. I currently have 250 but the WAN port on my ol' reliable g-router is 100. I don't need 250 so when Cox jacks its price, I'll downgrade to 100.
150 isn't available in your area? Look for Essential Classic at the link. Cox may just be hiding it from you.
Let's take UHD movies as a standard. Most streaming providers recommend 25 Mbps to stream at UHD. To compensate for Network Overhead (network management & re-transmission of packets), 100 Mbps would sufficiently allow 3 simultaneous UHD streams.
You probably wouldn't stream 3 movies at the same time but it gives you an idea of the adequacy of 100 Mbps. If you bundle your services (phone, TV, Internet), you may not find a bundle with 100 Mbps...so watch for this.
www.cox.com/.../speeds-and-data-plans.html