Thanks for the suggestion.
Are there cheaper ones than this that you would not go or are you talking about the DIY ones with software and a PC?
I can't find anything less expensive (but still a current/supported QTS/QNAP product) today. I would suggest to max out the ram on this though as a very inexpensive way to get the full use out of it, even for just home theatre use.
To me, the DIY boxes are not worth it in the long run when your time is involved (at least not when my time is involved!). They may be negligibly cheaper to build, hardware-wise, but their cost goes up just as their reliability goes south too. I have customers with QNAP products which are running for almost a decade now. Haven't seen any DIY project keep working after that length of time. Of course, HDD's have been replaced in the meantime, but they rebuilt the arrays without user intervention and without any data loss.
The DIY boxes have (and use) more power, are more general purpose vs. a primary storage-based unit like QNAP offers, offer no support when (not if) things go awry and considering that the biggest cost is the HDD's themselves, offer very little savings in the end too.
If this is a second or third storage option with important data on all, then DIY may be an option.
If this will be the primary storage option for all/most of your important data, DIY is the path I would not
choose, from experience.
Edit: Just want to note that reading about Synology, they also make the equivalent products in terms of reliability to QNAP, I just don't have any long term experience with them, myself.