I'm surprised no one has answered yet, it seems like everyone that uses KVMs has strong opinions...
I'm most familiar with Raritan, and they have equipment that will do what you want, but you might have to mix and match to put together all the stuff you want. One downside for us was that they didn't have any local reps where we are and it wasn't satisfying talking to them on the phone to figure out what products would work for us.
(Avocent, OTOH, had salesman who'd come in and look at what we wanted to do and come back and tell us what they had that would meet our needs.)
Raritan has two main lines, analog kvms and kvm over IP. We're using the analog line, and have daisy-chained switches together to get the ports we need using their older products (the MasterConsoles). If we were starting again, I'd go with the Paragon line (analog) or Dominion (ip) because they're more modular.