Plex server and NAS rack mount build

Hi. New here. Been reading a lot of the guides but wanted to ask for recommendations for my specific use case.

The suggestions from my wife that I clean up all the junk in the office are also starting to increase in both frequency and severity so I thought now was a good time to upgrade to something a little more powerful.

I run a small plex server on an old i3-4150 Windows desktop that is starting to show it’s age. I have 3 3.5 sata drives for media and 1 sata ssd for the os. Media drives are 8TB, 6TB, and 3TB that I’ve collected over the years. Drives are all at about 75% capacity. I’m willing to replace the smaller capacity drives with something larger if needed, but would like to be able to hold at minimum 4 drives in the chassis.

My end goal is to separate the storage from the plex server, then virtualize the plex server and another workstation that runs sonarr, radarr, ombi, and a few other low power processes into the smallest form factor possible. If rack mounted isn’t the way to go I’m open to other suggestions. This build will most likely live in a closet, so depth is limited unless I mount the rack sideways. I share the office with my wife who works from home and she is not a fan of computer fans spinning up while she’s on a conference call, so noise is also something that needs to be considered.

Plex is mainly used locally on an Xbox One attached to the living room tv, a 4k fire stick in my bedroom, and my daughter’s ipad. I’ve shared the server with a few family members, but my upload is only 10mbps so while I would like to be able to support 4 or 5 concurrent 1080p streams bandwidth limits what I can actually provide outside the home. Local streams take priority over remote. I don’t see local use growing past 3 streams anytime soon. I would like this build to be last me several years before another upgrade is needed. I think I put the current server together about 8 years ago at this point.

Here’s what’s in the Poweredge. If these parts are servicable for what I’ve outlined here I would like to reuse them.

Xeon E3 1230 v2
Dell 0PM2CW motherboard

I have a 1TB Samsung 860 ssd I can use for the boot drive.

I have little to no experience outside of a Windows environment, but am willing to switch the os to something else if the performance increase makes it make sense. I’m not afraid to learn something new.

I would like to keep the budget under $500, but if that isn’t realistic then I’m willing to increase it. This would not include the cost of a server rack/cabinet if required.