yup unraid is not free but I can run my games and nas on just one CPU. not sure if freenas got this but unraid can add additional storage easily.
ya the advantage of getting ds416 is saving all the hassle but you'll get a lousier performing system.
I'm using Synologies
and moved on to PC NAS
Firstly, a NAS is a NAS, not a multi purpose device
If you intend to play games / do work on your pC, and let your PC have NAS functions, you are simply inviting danger to your data
For NAS
Look for a low-powered Mobo and case
I went with the As Rock J3455 ITX mobo but there are cheaper ones like MSI N3160, all of which are not available locally
Choose a cheapo raid card
Settle on your casing ( i went with an old Lian Li Q25 i had lying around )
Ultimately, i am going for fault redundancy so i went with Windows 10
The main advantage of a synology over a pc setup
Available Apps to access your NAS
Ability to sync multiple Google Drive accounts to your NAS
Above two is solely the reson why i still use a synology for work.
If you are the sole user of the NAS, the apps won't be much of a concern. But if your GF / Parents / Siblings / friends also need to use the NAS, explaining the connection process, AND assising them can take a while..
Advice is to ask yourself if you are willing to learn to support the NAS in the event of total failure. If you willing, take any NAS OS and go try it out.
If NOT, stick to what you are comfortable with.
Those who have experienced NAS / HBA failures will understand what i mean when i say that the feeling of being totally helpless when you cannot access your data when you need it most, is priceless.
And when you have to deal with a support ticket system when the mfr has no phone support is @#$#%#$