You can use SSH to remote into the Core via command-line. Under Windows I use Putty. To get a UI you need to set up an Orbiter on the remote PC (you do this through the Pluto Admin webpage and download the Windows client from there as well).
for more information on Orbiters. Note that using an Orbiter isn't exactly like VNC, but rather allows you to control the Core. However, from a UI perspective it's pretty much what you get on the Core/Hybrid with the exception of Media Playback (which you probably wouldn't do over VNC anyway).
Hmmm. Well, I read in another post that a user wanted to setup more than one video capture card to work with Myth, but got a reply back that it is difficult to do in Pluto, requiring manually configuring it. Thought that might help. Also, during my testing, I've been shutting down the system during the day (while I'm at work), and seems to only way to do that was at the console of the core machine (and non-obvious to an seasoned Windows user). Again, hoping to not have to always run a monitor on that computer, but rather access it remotely.