I am getting optical fiber to my house. I will also be buying a DS 1522+ (or similar). To avoid speed problems I might be buying an 10 Gbe card for the NAS. As 10 Gbe routers are rare and expensive 2.5 Gbe might be enough. Now comes the question. What kind of router do you recommend? It could be a cable router and I could have the wifi as a separate unit(?). The routers normally have only one 2.5 WAN and one 2.5 WAN/LAN. If I connect the incoming cable to the WAN -port that leaves only one to connect to the NAS. Then I should connect the PC to the remaining 1Gbe LAN ports. Will I loose the benefit of the 2.5 Mbe if I work with pc that is connected to the NAS via the router? So which router to buy? I would need max 5 ports.
You only need a 10GbE router if you have a >2.5GbE internet connection. Otherwise get yourself a 10GbE switch and connect all your devices, and your router, to that.
Unless all your (max 4) devices are going to access it at the same time (unlikely) you won’t see any benefit though.