Going off the local PC only idea, you could script just your rebuilds of them in the off chance something goes south, along with maybe a disk image with the majority of common games loaded. This is just thinking along the lines it's friends and family, not the general public. I'd probably use gigabit Internet (or more) which makes updates you're missing fast, while Steam lets PCs on a LAN share updated files and save bandwidth.
Did you consider patch panels or things like PatchBox to organize those UTP cables or allow for changes in your switching later?