Portable SSD or NAS ?

I'm in need of a reliable relatively fast back up for my main household system. After looking at better quality portable SSD drives (4TB) I found the price high enough that maybe I should just implement a household NAS that would give me back-up and more.... Thoughts?? On another note, I've got a 6TB LaCie external storage unit I was using for a Mac that I could disconnect but it has a Thunderbolt 1 interface. Any idea if this could be used with some form of adapter? I've not found anything a decent adapter that connects to the Thunderbolt 1 spec.....