Networking setup for an apartment

Hello. I need some help regarding the network setup for a small apartment building with probably around 10 users. Some of which I am assuming to be p2p users.

Our previous setup was a single wireless N router (Buffalo) on a 160/10 Mbps connection. Sometimes, our router restarts by itself so we lose connection. Often, Skype is slow and for those playing games, the network is slow even if they are all local.

After that, we changed our setup to use two wireless N routers (Buffalo and NEC). The previous 160/10 Mbps cable connection on the first router and a 100/50 fiber (?) connection on the second. It got better but still, while one router is fine, the other router is bad. When the bad router restarts, all connections probably shift to the ok router so it goes bad and restarts also.

I read from the Internet that maybe it is because the router cannot handle the number of connections. I have asked them to reduce the number of connections on their own clients, scan for viruses etc. but not much improvement happened.

Also, I wanted to buy those Cisco gaming routers from the US which apparently can handle more connections but I was informed that I could not use them in Japan due to some legal issues (?). So I bought another router (Corega) instead, so now we have 3, and two internet connections.
I also checked the open source router firmware but I cannot install them except on the Buffalo one I think so I haven’t done it yet.

It is setup as follows:
Internet 1 – WAN Buffalo LAN – Corega
Internet 2 – WAN NEC

Some info:
Two floors, row of apartments
Routers are placed in a common area somewhere around the middle
Signal strength is from average to excellent, depending on distance
Everyone connects wirelessly

I asked my company’s system administrator for help and he already suggested the setups I mentioned above. And after that, there is a current suggestion of using a desktop PC for a router, a hub and connect the routers as access points there. It’s a little hard to talk to him but what do you guys think? Will this contribute to a significant improvement?

The company provides the equipment and the connection so I'd prefer to find a fix for this. Failing that, I'm close to leaving this hassle behind and just get a separate one for myself.

Please inform me if additional information is needed, thanks!