> I don't think Intel boxen (nucs) are upgradable very much.
Not much outside of ram or disk. If you want a real system for expansion, get a real atx form-factor system. If you need a very specific use-case, get a nuc, pi, or other form-factor.
If a general desktop, buy as big as you can afford, and leave some room for expansion - just start with a standard atx if your first time.
If you want gaming, throw money at the video card, with moderate ram (8-32gb). If you want to do more virtual builds as you said with docker and vagrant, leveraging virtualbox or qemu/kvm, go for more 16-128gb of ram. Get as many cores and as fast a cpu as you can afford with them, plus as much ram as you expect you need.
I do both gaming and using mine as a server. I tossed the 1070GTX in it, and 128gb of ram with 20 cores, a few M.2 disks, and I want for little. I game a lot, and run whole domains and ecosystems of vendor appliances internally as vm's on it, and it chugs along in most cases. I added some left-over ssd's and spinners I put things like games and non-essential vm's on, just in case they die, which I anticipate they will do as most are orphans from a like-mate disks already dearly departed.
Surprisingly, gaming hard on it and running a half to full dozen vm's or more on it do little generally to shake it. I'd not expect a typical windoze box to handle anything like this, power of linux imho.
If anything crashes at all, it's usually the DE compositor freaking out after a few months of uptime. /me coughs "Thanks KDE/Cinnamon."
-mb