Well for an OS to use the 4GB, you want 64bit, and only Vista 64 is the only real option for the software you'll be using.
And I'm surprised you haven't squeezed in a large (20"+) monitor in there. I do this kind of work on my computer, and I am dying for a larger monitor than my 17".
And I'm surprised you haven't squeezed in a large (20"+) monitor in there. I do this kind of work on my computer, and I am dying for a larger monitor than my 17".