You may want to read this thread here (if you haven't already):
http://yabb.jriver.com/interact/index.php?topic=42936.0MC is very adept at using multiple monitors, and it remembers detached display settings on a per-zone basis (full-screen or not, position, size, and which monitor are all remembered). However... For performance and ease of use, I would strongly recommend considering installing multiple PCs in each place where you want video terminals and running MC locally on those machines. Multi-room audio distribution will work perfectly off of the central server. For video, you're going to end up needing to build a god-machine, and even then, running multiple videos in separate rooms is going to cause performance issues (especially if you decide to ever get into HD video sources).
Where instead, a small 15" or 17" touchscreen running either Netremote or MC's Theater View in each room, then also connected to a nice big LCD/Plasma HDTV, is going to be sweet. You don't need big or powerful machines in each room. Simply something to run MC, girder, and maybe Netremote. The file storage can
certainly be on your central machine that does the audio distribution for the non-video-equipped rooms, so these remote machines just need to be "terminals". Any reasonably-equipped PC will probably do it, so I'd look at form-factor (small and quiet). One nice little bonus is that JRiver lets you use the same license for MC on multiple machines (so long as you own them all and don't abuse the privilege), so you only need one "copy" of MC anyway!
Other problems I see with distributing video from a central server (other than performance):
1. Video cable lengths. VGA is limited to 20' - 30' after which you'll end up needing to buy distribution amps. Using baluns can compromise video quality, especially with long cat5 runs. You're essentially almost just as length limited with them, though they do give you a bit longer distance (not terribly much though).
2. Input cables. If you need to direct-connect any input devices to the central server, you could run into length issues again. USB is tough to extend. Even the "active" extension cables are usually limited to 80-90' max.
3. Incredibly complex control will be needed to properly route video to each room. You won't be able to use MC's Theater View (see the thread I linked to above) and recreating it's functionality in Netremote may be an exercise in frustration. Even if you succeed, they're sure to add new features to MC and Theater View which you'll end up missing out on (they release new public builds of MC with new features almost weekly).