You can use nas4free or freenas to make your own nas for much cheaper as well as much higher performance.
The operating system installs to a flash drive so it doesn't take up a valuable sata port.
Get something like:
"Dell Optiplex 390 MT PC Intel Core i3-2120 3.3GHz 4GB" for about $100 on amazon.
"or any old computer you have lying around from the last decade
Marvell Armada dual-core CPU and 1GB of DDR4 isn't a very high bar to clear"
and fill its 4 sata ports with the hard drives you want.
I use 4 - 2 terabyte drives in a raid5 or as nas4free calls it raidz and I upgraded the ram to 8 gigabytes.
It easily saturates a gigabit connection and is setup as an ftp server so I can "have access to data from anywhere in the world".
The ram that you have installed automatically acts as a read cache (arc cache) meaning if you constantly load the same file/game over and over it will be pulled from ram instead of the hard drive easily delivering gigabit speed (125 megabytes a second) since even ddr2-667, the oldest I can currently find in my room, operates at 5.3 gigabytes a second. Newer ram obviously runs even faster but for the purpose of a read cache as long as you have ddr2 or higher you should be good.
More important is how much ram you have.
You can install a solid state drive and have it at as a write cache (zil cache).
You can and should always have data compressed on the fly using extremely fast compression (lz4).
You can even enable deduplication if you are in a position that needs it, but you need to do your homework before enabling.
If you are going to buy a nas you might as well start with the cheaper one with more features and start learning there.