As another data point, the quality of your in-home wireless can be part of the problem as well. Especially true if you have a wireless device that was provided by your cable (or DSL, or Fiber) company... most of them are okay but not great.
Even with a good wireless router, and decent wireless adapters in end-user devices, there can still be issues with overcrowded wireless channels, particularly if you're in a neighborhood with many wireless networks in sight. Then, there are also things to consider like the layout and construction of your house, relative to where the router and the end-user are each located.
The problem often times isn't about bandwidth... as you noted you're on the highest tier TWC offers. For many people the issue of a good net experience is no longer about the last mile to a provider, but is more about the last 30 feet in your own house. Though not ideal for long-term usage, try plugging the laptop into your router directly with an ethernet cable, and see if your issues go away... that will give you a good litmus test if it's your in-home wireless that is the bottleneck.