If, as you recommend, no one is using the "main computer" in a peer-to-peer network, is there any reason why a server-client network would be faster or more reliable?
I'll take a crack at this question.
Servers can enforce consistent policies across all of the computers. They can also do auomatic backups. All of you personal settings are maintained on the server so they are consistent from one computer to the other. The server can serve as the DHCP server. The server can also be an internet firewall. The server can set up domains which will allow more computers than peer to peer and may allow faster traffic if you are pushing toward the limit of 10 computers on a peer to peer.
As you see there are a number of roles the server can function. They can all be done by other programs as well, but they are in one box. I chose to let the router be the DHCP server. All key documents are kept on the the server and are backed up peripherally. If one of the computers goes down, it will take me somewhat more time to replace it, but I am looking at some new options. Speed has not been a problem with my 7 computers on the network.
Any more uses Bert?
Is your system only slow when with internet, or is AC affected. If it is the latter, you might need to check that you don't have either 2 computers with the same name or IP address or that you may have a bad NIC card on one of the computers which can screw up the entire system.