Internet through a NAS and Time Capsule I have tried to use my Time Capsule as external storage and backup but finally realized it's not working very well. It is very slow.

So, I think I'm gonna buy a Synology NAS as most people recommended. Maybe a 215J.

Today, I have my modem connected to my TC acting as a fast router. That works well I think.

My question is, how do I connect my internet for best effect if I get a NAS? Modem > TC > NAS? Or how does it work?

Additional comments are welcomed!
The NAS won't have any routing ability so it's pretty sure that it won't be directly connected to the modem.
Your schema is what I recommend. I have exactly the same architecture with a modem, an Airport Express and a Synology DS215j.

Modem ---------------- TimeCapsule (as router) ------------------ NAS
       WAN Interface               |              LAN Interface
                                   | LAN / Wi-Fi
                             Other devices


You may need to configure your TimeCapsule to make some Port Forwarding if you want to access to your NAS from outside of your network (I highly discourage that because of network security issues).

That all for me.