Will this be overkill or otherwise not recommended for someone who is new and just starting to learn?
My goal is to have something I can grow into, but initially I'd like to host a few VMs, game servers, and a have place to store content. I'd also like to host a PLEX server in the future as well but might buy a separate piece of hardware for it specifically down the road. Thanks in advance for taking the time to help a newbie!
$400 for that seems steep. Go look for an HP Z440 workstation as cheap as possible and upgrade it. A 12 core E5 v4 cpu is literally $5 and you should be able to pickup a chassis with cpu and like 8gb ram for ~$120. Then for $10 a stick but as many 16gb ddr4 ecc dimms as you want.
For $400 or less you could get 12 much faster newer cores, a basically silent workstation that idles under 100w and 192gb ddr4