

On low end CPUs you can max out the CPU before maxing out network—if you want to get fancy, you can use rsync over an unencrypted remote shell like rsh, but I would only do this if the computers were directly connected to each other by one Ethernet cable.
Regarding DNS servers, what router do you have? Some routers have simple enough DNS capabilities — I have a MikroTik, and have it set up with DNS entries for internal services (including wildcard). Publicly accessible services just use my registrar’s DNS (namecheap — no complaints).