I’ve built every NAS/home server I’ve ever had. There’s lots of options out there for the case as well. You could take an SFF Mini ITX case with a single 5 1/4" drive bay and put an icy dock 8 x 2.5" SATA backplane in it. Don’t know if icy dock (brand) is widely available in Europe…
Just pointing out that if you imagine it (form factor with 8 hot swappable drives) there’s probably a solution to build it from scratch.
That looks an awful lot like what I have. I’m using the Lian Li PC-D600. I think I’ve managed to get my hands on one of the last ones in the wild. They aren’t even available used on eBay anymore.
What I like most about it (and the Tower 500 that you linked) is that the motherboard is on one side, and the drives are on the other. Keeping the drives cool is easy, I just upgraded the fans on my SATA backplanes and the case, and even under load the drives run very cool.
You can have this case when you pry it from my cold dead fingers.
I started with Plex, but I would say it wasn’t until I spun up Nextcloud and got it running that I really would say my life changed. My entire family now has Nextcloud accounts, a family calendar, instant upload of pictures from my phone, all my recipes, and I even have OnlyOffice document server running for editing documents in Nextcloud.
Family and some friends from back in my days in the military. Those guys are who I keep an eye on, because they don’t use it as frequently as my family.