Is there a solution for building a network in the office based on a local cloud?

Question

Computer networks

A small office of computers for 20 plus a couple of MFPs. Now I use a couple of WiFi routers for the network and a shared folder structured by projects in Dropbox, the file size is now 100GB. Work goes with documents, so there are no heavy files.
Everything would be fine, but Dropbox is a buggy thing, and in general, local file sharing is needed, without going into details.
The standard output is clear: a decent router, wires, a dedicated computer with a raid array will solve the problem.
Question: is there a working, good bundle of hardware and software on the market that will allow:

• combine all devices into one network not by wires, but via WiFi;
  
• synchronize over a local network, and not over the Internet, data on all computers, and not have one network folder?
  

That is, is it possible to put one good router with WiFi (router - because there are two sources of Internet - wire and Yota, one or the other works), which will pull> 20 wireless connections. At the same time, super speed is generally not needed, because everyone has a copy of all the files on their computer and you don’t need to constantly access the network storage (we also have enough Dropbox sync speed, but here it will be faster in LAN anyway) , mega-fast Internet is also not critical for everyone, normal access, no one needs to watch movies at the same time and download non-stop.
Plus, plug a computer or a decent NAS into the network with some decent software that reliably synchronizes data on computers. Also, this computer or NAS synchronizes the same data with a cloud on the Internet, like the same Dropbox for those who are not in the office.
Does anyone have real experience with such networking? Whom we do not ask, everyone can not say anything intelligible. So you don't want to pull wires. 2015 is in the yard, as much as possible ...

Answer 1

In the office, wires are better - usually there are too many wireless routers in the area, they interfere with each other. If Wi-Fi is still required, take a cheap microcurrent, networks can be demarcated, including through virtual-ap.
And at the expense of disk storage - any simple server that will have a harem folder and it will also be synchronized via dropbox.