Gubbgnutten
I think you might be happily surprised about the performance of store bought NAS. I have an old WD myCloud that I use to currently backup my photos. It's pokey slow, no doubt, but it works. Directories take a few seconds to load but nowhere near the 5 minute Mac load times of my unRAID server. I'm sure a Synology like the ones John_M recommended would work just fine. I was hoping to save a few bucks and have more control over the hardware though, so I investigated unRAID. Maybe even be able to work directly off of it instead of a local drive. I think we all agree tinkering with this stuff is fun, but at some point you have to actually get work done.
In the end, a server has to be consistent and dependable. I would most certainly trade off a few MB's of read and write speeds for a consistent experience no matter what the client I use.