On the other hand, for the graphics card, it's mainly to do my diploma project so I don't necessarily want to invest in a quadro 2200 to do a complex project and then small sets.
After having a weaker configuration can run the software too, but it can take longer to do some operations. If it's really too slow, just reduce the graphics options. By the way, why Inventor and not SolidWorks?
@gt22: Thank you for the link, indeed there are pretty good offers, I'll think about it.
@ .PL: Yes for sure, but for the moment I have a laptop with a not so great graphics and 500 to 600 pieces it still runs without too many problems. Inventor because it's the software that is used in my school (and which is pretty well done I think).