I use an HP microserver gen 8, which I bought second hand (300$) and upgraded with a better CPU (20$ from ebay) and extra ram (80$) and 4 2TB SSD’s (100$ per). I installed Windows server on it because I just wanted it to work in a way I’m familiar with, but a colleague of mine installed Synology OS on it. You can use the cd drive bay for the OS disk (with some tweaking). Since you already have the disks, this would fit your budget.

I just use an HP Microserver gen 8 with upgraded cpu and ram. But yea, just a relatively cheap computer is all 98% of the people really need, as long as you can configure enough disks. NAS’es are way overpriced with shitty hardware.

Microsoft needs to get its shit together because reboots were a huge point of contention when I was setting up automated patching at my company.

This is way too accurate. With a buddy I even have what our wifes call playdates, where we are messing around with proxmox, containers and linux distros. We both have some old poweredge servers, laptops, raspberry pies and old phones to mess around with. Nothing useful has come out of that so far, although we’re preparing a lemmy and mastodon instance, so we’re getting there.