Media PC and Desktop PC at the same time?

I'm trying to get the functional equivalent of a networked media PC and desktop PC while using just one machine. I believe my computer is powerful enough to do everything I want simultaneously, but I'm not sure the hardware and software available can do the job.
What I have is this:
Station 1: A pair of small pc speakers and a monitor on a desktop at one end of the room, with a wired keyboard and mouse.
Station 2: A television connected to my video card via HDMI, audio from the TV sent through a stereo receiver to stereo bookshelf speakers, a wireless radio keyboard and mouse.
Right now everything works at both "stations", but not the way I'd really like.
Here's what I'd like to do. At the very least, be able to see and hear one app (Firefox playing YouTube, a movie on Media Center, etc.) at one "station", while using another app with audio at the other. Ideally I'd like to be able to use a dual monitor setting other than Clone or Extended Desktop, since neither really describes what I have, and I'd like to set each screen with a resolution that works best for that screen (right now I either have tiny text on the TV or huge text on the monitor). Better still would be the ability to control each "station" with it's own cursor.
The idea is, for example, for me to be able to watch an internet based video on my TV at station two, using the mouse to control playback, while my wife, at station one, can check her email or play a PC game with sound. As it is, if we're playing simultaneously, we have to take turns with the mouse, and all of the audio goes to the Windows "default device", so only one of us can enjoy sound, and it's often more sound than my wife or I want.
Has anyone gotten anything close to this? I know it's possible, but I don't know if it's available.
Thanks!
-Adam