Answer for Old Router

Simply the fact that your router is 6 years old is a good reason to replace it. In my experience, routers do not age gracefully. Either because of performance or age-related failures, I’ve observed that after about 3-4 years, most routers are past their prime.
If you simply need to cover high-speed Internet service of around 100-200 Mbps, then any gigabit router should work. I generally use the Linksys EA3500 router, as I am familiar with how that router operates. It is usually around $100. But any similar router from Netgear or D-link, etc., should work as well. If you have a house of Apple products, then you should also look at the Apple Airport Extreme router. It is more expensive (about $179), but it is easy to set up if you have Apple devices in your home, plus it is a very high-performance router. FYI, it works with all devices, not just Apple devices, but I find that people who have Apple devices find it easier to set up.
If you are looking for something higher performing and you do not have Apple devices, there are many options you could look at. But I assume you probably aren’t looking for that type of performance.