Suggesting for Organizing a "Networking Shelf"

I've been brought into a small medical office to help set up a Mac fileserver. But you know, theres always little overlooked details. In this case, that would be "where is the server going to go?"

So this is the area where it need to go, and where I also need to clean things up a bit. ( https://i.imgur.com/16Q7Dsu.jpg )

The server is going to be a Mac mini with a Mediasonic 4 bay HDD enclosure. I'll most likely get some kind of stand for the mini so it can be vertical, to avoid things getting stacked on top of it.

Going down the list of items:

1. This is their PC server. I don't know what it does and I have nothing to do with it
2. Some piece of non-computer related electronics. I'm not sure if it's something we can remove or not.
3. This appears to be a DSL modem, which doesn't make sense because I don't think they are on DSL. It would take weeks for a single software update if that were the case.
4. This is a linksys router, they probably use it's wifi.
5. This appears to be a FIOS router, but it has no coax input, instead it has ethernet input that is connected to the DSL modem looking thing. Also I'm sure both of these routers are broadcasting wifi on the same channels right next to each other.

So in addition to adding a mini and a drive stack, all of the ethernet ports in both routers are full. There is talk of hardwiring many of the workstations in the office, since shared server and backups over wifi will be painfully slow. So given both of those facts, I'm just going to install a 24 port ethernet switch NOW even if we're only using 1/3 of the ports.

One thing I know very little about is IP based phone systems. If they are using one of those, will moving things to an unmanaged switch that is connected to the router (as opposed to being plugged directly into the router) cause any issues?

What I'm looking for suggestions for the most, though, is physically getting everything in here. In such a way that everything breathes and nothing overheats. So I don't want to stack things on top of the switch, and on top of the mini. Originally I was thinking of getting 2' zip ties and zipping the switch to the bottom of the shelf, but it has that weird bar in the middle that would interfere with that. So now I'm thinking, if I could find some kind of wire-rack mini shelf system i could stand up on these shelves, then I could stack all of the smaller stuff with even spacing and plenty of air flow.

I assume I can probably get rid of #5 but not anything else. In an ideal world, I'd have them put a big piece of plywood on an empty wall and I'd wall mount everything to that nice and clean.