Seriously consider one of the Ryzens. Some of the mid range models have excellent performance and low power consumption to the point that some power supplies won't handle how
little power they draw at idle. That makes it easy to make a nice quiet machine with low operating costs with an upgrade path if you decide that you need a faster processor later. Of course, if you need the performance, you can go straight for one of the higher-end grunty ones right now.
FreeBSD runs great on them (though the Vega graphics in chips like the 2400G still isn't quite supported yet but you already have a graphics card, right?) and I've been able to still run Windows 7 on the chipsets I've been using, though you do have to mess with it a bit. Most customers I have gone to running FreeBSD on the bare metal and then Windows or MacOS or whatever in a VM depending on their needs.
Definitely use an SSD if you're not already, and since modern software is bloated to the extreme and RAM is relatively inexpensive right now, don't skimp on the size of your first two DIMMs so you'll have space to upgrade later unless you go straight for the MAX that the chipset & cpu supports.
Try not to skimp on the motherboard, either. It pays off in the long run. I almost always use ASUS (occasionally 2nd choice is Gigabyte depending on feature set) and loved the Sabretooth line for general purpose to workstation class but they've discontinued that "line." Just don't cheap out on the board.