...but how about the monitoring?
I have an HDTV connected via HDMI from my GPU that serves as a fullscreen monitor output. My primary monitor is 24" LCD, which contains all the Premiere GUI components, and then the HDTV displays the same as the content of the Program Monitor.
All that is needed, at least as far as Windows 7 is concerned, is to extend your desktop to the second monitor, and then set your second monitor as the realtime External Playback device. The exact "path" to get there is Sequence > Sequence Settings > Playback Settings > Realtime Playback > External Device (dropdown) > select your device.
Looks like this in the settings:
But can I still run two GUI monitors at the same time - or do I need a larger 30" monitor to consolidate both current screens onto one?
Some people have made this work, but you need two GPUs to do it, and there are often cases of driver instability, etc. If you're using hardware MPE, your primary monitor has to be driven by the primary GPU, with the external monitor connected to the second output of the primary GPU; the secondary GPU would drive the third monitor. I set this up once as a test, and it worked, but because I had two different GPUs--one nVidia and one ATI--it was pretty flaky. I've been meaning to try it again, now that I have two nVidias, but hadn't gotten around to it.
That said, I've used a single 24" for three years, and really haven't ever felt cramped. I set a buddy of mine up with a 27" Dell Ultrasharp and at the high resolution it runs (2560x1440), it's a ton of real estate without the big footprint of a 30" LCD. Really depends on your personal GUI preference...