All of the above boards use DDR4 memory, you should double check which specific speed is best suited to your processor and motherboard combination.
There’s no need to go insane with memory on a home server, 8GB will be more than sufficient for the vast majority of cases. That being said, RAM is currently quite cheap so if you have money to burn you could always go for a 16GB set.
In almost all scenarios it will be better to go for a pair of matched sticks rather than a single stick, in order to make use of the available memory channel bandwidth.
This set from Crucial may not look as appealing as some other sets on the market, but it offers decent performance at a very reasonable price.
The last component needed before we actually get to storage is a power supply. If you’ve gone with a relatively low power processor with integrated graphics then our systems isn’t gong to draw a ton of power, even with 6 hard disks is only going to draw about 300 Watts.
That said, you never want to cut it too close when it comes to power supplies, and in any case most reputable manufacturers start around the 450W mark.
You’ll also want to make sure that your PSU has enough SATA power connectors for the number of devices you want to use. Most PSU’s will come with at least 4, but definitely check before ordering if you plan to use more drives than this.
This unit from Corsair is well regarded and will have enough power for most server builds. If you think you might upgrade your CPU at some point or add other functionality via expansion cards then you may want to upgrade to a higher wattage power supply.