Just a +1 for the Synology NAS products. I'm frequently amazed every time I use it how clean the UI is and how they basically implemented a full window manager for the underlying Linux system in a web app. It's exactly what a NAS should be: powerful and flexible, yet easy to set up and use, but rock solid even if it just sits there. Lots of great things to say about using it in nearly exactly this setup for about a year now.
Everything you say is 100% true, but be sure to keep the OS up to date if you expose any IP addresses (security cameras, etc) to the world at large. NAS boxes are just about the highest of high-value targets.
