Having mutiple routersin my house

How can I get a better signal on my wireless network to reach my basement pc and smart tv

Unless you use the Ethernet cable for any services, the router doesn't have to be located the same place as any of the PCs in the house. If you can place it in the center of the house rather than one end, that will help.

Like any radio transmitter, wireless routers have different power outputs. You can get a more powerful router. If your existing device is required by your broadband provider, you can output the signal from that one to a more powerful router via an Ethernet cable. Explain your situation to someone that sells them and they can resolve the issue.