It's really all about what you do with your computer but generally the capacity of your hard drive does not slow your computer down. If you think you might fill your hard drive up, maybe it's best to put two hard drives in your computer, an extra for your operating system. I use a 2TB hard drive and a 128GB solid state for my operating system so when the computer boots up, it does it faster. If you're talking about overkill, I am starting to think 2TB is a bit less for me and 4TB is the perfect amount. It would probably take me a bit of time to fill that up...