The problem is we don't know what the capacity is. You can have two year old Dells with 512MBs of RAM or 5 yo computers with 4GBs of RAM.
We also don't know your OS? If you have XP Home and are limited to five connections that could be why it is "going down." We don't know what "going down" means.
It's like a history. You have to give us a history and ROS for us to know what is up.
As far as a server, a Dell T310 should be all you need.
I have to admit though, these questions always kind of make me wonder. You are asking a group of users, all with different setups and networks and servers to suggest what is best for you.
It is almost like my coming on here and asking everyone what car I should buy. What color do you like? Do you like a fuel efficient car or not? Do you want a foreign car or American made.
http://amazingcharts.com/support/hardware-os-requirements/These are the minimal requirements as AC states them. Notice there are no Home versions mentioned. Only Pro.