Apple Airport and Storage

I have a similar size house and have thought about doing something similar. I never got around to it and honestly, I'm not sure I'd gain that much. I have a pretty strong signal on my second floor. My router, which is an ASUS RT-66U, is in my basement.

This support article from Apple should provide you with your answer, if not more questions. I find it interesting that it can have an adverse effect.

Adding Wi-Fi base stations when it is unnecessary can reduce Wi-Fi throughput because the Wi-Fi network will require more data management overhead. The network configuration also becomes more complex. In the case of a wirelessly extended network, throughput may be reduced to less than 60 percent of that of a single device. The general rule is to keep the Wi-Fi network as simple as possible. You can accomplish this by using the minimum number of Wi-Fi base stations required to service the physical network area and by using Ethernet wherever possible.

You might want to think about the current position of your Time Capsule and if there is anything you can do to improve the location for the widest range throughout your home.