Preferred Service never gets near 50mbps

Hello,

I upgraded my internet service plan  and modem months back, thinking I'd get better speeds, but upgraded service and modem yielded the same speeds, so I returned the modem and downgraded my service back to preferred. I saw buffering issues with streaming from time to time, but nothing I couldn't live with. I couldn't see spending the money for a new modem and upgraded service when my speeds were the same.

The last couple of weeks I start having issues with gaming. I did a lot of troublshooting for my Xbox One and nothing has helped. I thought i'd revisit upgrading my modem again.. from DOCSIS 2 to DOCSIS 3. Again I'm seeing the same thing.. my internet speeds are consistently around 30mbps when I do speed tests. I am testing using an ASUS RT-N66U router and wired connection. 

Can someone look at my account and see if there is latency or an issue with the way my account is coded/setup? I would like to get the performance I'm paying for and hope there is a way to clear up the latency, so I can do online gaming. The latency I've been seeing makes it too aggravating to play online games.