I'm looking for recommendation on what hardware to get to get if I want a silent (or very nearly silent), very low power NAS server with at least four usable hot-swap drive-bays in a case that's not too large. I want to be able to leave it powered on 24/7 without worrying too much about electricity costs or the heat generated from the machine. It doesn't need to be ultra-fast or to have a sleek and sophisticated appearance. I'm not penny pinching on the cost, but don't want to waste money unnecessarily.
If it helps people understands the sort of thing I'm after, I would probably have bought a Helios64 rather than building something myself if they were still operating. I'm not adverse to buying something similar pre-built if there's something else on the market, but I'm not aware there is. Some sort of ARM hardware sounds like the way to get low power consumption at an affordable cost, maybe even a Raspberry Pi. Thanks in advance for any advice.