c7000v2 not getting full speed

Don't just look at your modem/router for speed issues even if you upgrade.  You need to check the your network module's or network chip set on your motherboard for its speed limitation.  The bottle neck will reside with your network card/chip capabilitites.  If you can only go 100 Mbps then that's what you'll get.  If you absolutely know what your network card/module is capable of and your not getting the ISP provided speed along with your Router/Modem or combined Modem/Router's device, then look for the Router/Modem's speed limitation in it's documentation and also on the original box it came in for speed values you should be able to attain.