Peter, thank you so much for your post and the information!
That router is gigabit capable, and at least two of the office computers are as well (The Photoshop and video editing computers). I'm not sure about the others, though those two computers would likely be the only ones sharing large files anyway. That little 5-port Linksys switch is NOT gigabit capable. Good catch, I'll order a second Trendnet TEG-S80G for the office systems.
I have no idea yet what has dhcp or not, except to say that all of the components in the HT have, at one time or another, gotten on the web for firmware updates and such, (though it's been sporadic) and I've never had to manually enter an IP address. So, in hindsight, I guess they do!
