We have a Linksys WRT54G WiFi router in our office which was working great when we had 5-6 folks.
Now on peak days we have 10-15 people, each with a computer, smartphone, etc, and an ooma VOIP device. On average 1-2 times a day I need to go hard reboot the router, and sometimes the border router (Cox-supplied device).

I assume this is just because the router cant handle this many concurrent users.

So my question is can these consumer routers handle this kind of load? If not, would adding more devices solve the problem, and how close proximity can I put 2 routers without having interference problems (our office area is not that big physically)?