I’m looking for an off-the-shelf 4 or 6 bay NAS with upgradeable RAM that runs TrueNAS (for ZFS). The QNAP TS-664 looked very nice, but the price of the 4G version (with 2 RAM slots) is currently 25% more than the 8G version (with soldered RAM). I’d like to have 16 or better 32GB of RAM.

Do you have any recommendations?