i would say that there could be an issue in the configuration of the router if your seeing slow down after connecting to the 4500 vs direct to the cable modem. If you don't game then you can turn them off or not use them. However some of the other settings might help. Check on the firewall settings, DNS, DNS Relay, things like that, it's all listed in the sticky.
The router should work well out of the box and not slow the speeds down when checking. I use speedtest.net for a quick check.