Are you in search of a "solution" when you appear to have NOT identified a "problem"? Are you editing video now? Is it too slow for what you need? Are you making artificially unreasonable assumptions about how fast video rendering should be? Can you change your workflow to reduce or eliminate high-end solutions to a low-end requirement? For example to let videos render overnight while you are sleeping (or over the lunch-hour when you are eating, etc.)
Your question very much seems like a solution in search of a problem. That is typically followed by an ill-considered waste of money.
Are there fast solutions to video rendering? Certainly. Do people need that kind of solution? Yes, of course. Do YOU need that kind of solution? You have presented no evidence that you even know how fast videos will render on your current hardware, and whether that is insufficient for your (also unstated) requirements.
I must agree with the other responses that anything going through a USB2 is dead in the water if you are seeking truly fast video rendering. It is just a joke.