when it says "shared", it means that the main computer RAM and the video card memory is the same memory; I mentioned before that it is not good because it isn't; it will slow down your system overall. dedicated memory in relation to the video card is something that is pretty common in desktops, but relatively rare in notebooks; the under $1000 HP one I mentioned earlier had dedicated video memory.
The Video card is mainly for games; poser 4, poser 5, lightwave, 3dstudio could care less what type of video card you have.
OpenGL is a feature set that a video card can have that enables it to communicate with the system; some video cards are better able to handle it than others. matrox historically handles it best, but Nvidia is pretty good.
Poser 6 uses openGL for previewing your work, as you work; it gives you more of a "what you see is what you get" experience. you don't have to use it, and allegedly Poser 6 will then act just like Poser 5 at design time. it does not speed up your final render time.
Vue requires a good implementation of OpenGL; in my personal experience, Matrox G200 handled it great, Nvidia Geforce2 was just buggy but worked, Geforce4 works great, and ATI 9700 was flaky.
Essentially, except for in vue, your video card just doesn't matter. Some graphical applications are starting to play around with using the graphic processor in the video card, but none you mention that you are likely to use (correct me if i'm wrong, here, folks; I haven't been paying intense attention to the subject for the last 4 months).
The system you mentioned, momodot, would handle things adequately. the only weak point IMO is the shared system/video memory.