Thanks for the reply. My follow-up didn't appear to get posted, so here's another attempt.
I've looked at DVRs, and they won't cut it. We'll want at least 30 users viewing feeds simultaneously. Each will view a subset, but each camera will be viewed by 10 people. Combining multiple feeds saves bandwidth (since we'll make the images smaller) and ensures they are in the same order for everyone. That makes configuration of each station easier, too.
We'll want all channels recorded (2-weeks of HD video per camera). PCs are easier to maintain for us, since we have hundreds of them. Fixing them is also much easier, and adding storage is very easy (e.g. a disk shelf with several hundred TB with RAID.)
A video proxy is sort of what we want, although one that combines it with recording would be more convenient. I just can't find details on products that do this. I have looked into HIKVISION based on your comment, although the web site provides almost no useful information as to the capabilities of the software.