Hi Mark, pretty much any card from nVidia or ATI/AMD will do, really...

My main recommendation would be to get one that's not too old, say like not more than 3 years old and you should be fine.

With newer generation cards, even the low end least expensive ones actually have plenty of horsepower for running MoI.

If you plan to do somewhat larger and more detailed models then you might want to get something in the mid or high end range instead of the least expensive models.

- Michael