I think what you are seeing is not the 'required' Vista footprint but the amount of memory that Vista is using to give you 'smooth', optimal performance.
I have a 4G system and with NOTHING running, task manager shows that I only have 76M free. I am sure it is using all available memory for pre-fetching; that memory which is just sitting around, not doing anything productive...
Whenever I load one of my normal working programs, it loads immediately and memory never appears to be running low. The opening screens of my standard apps just pop up. My programs start much faster than I have ever seen in XP.
I'm glad to see that you got your system running.