I'm running a small windows peer to peer network with an SCO Unix server. Presently, I have 3 hubs, all 8 port. I need to expand the system. Do I need a repeater if I add a hub? Or can I replace the 8 port hubs with 12 port hubs. I've got a vague idea of data transmission limits and I feel like I'm well under them distance wise. (longest run from a hub is 30 50 feet)