Here's a speed sculpt I did to test out how to render highpoly meshes in Marmoset. It works VERY VERY well. I think that Marmoset has a real shot at stealing some of Keyshot's market if you guys keep working on it with that aspect in the back of your head. Can't wait for the next update :)
Toolbag2 seems like a great solution for high-poly shots, Keyshot has always been a too expensive for me. I loaded a 700mb obj fine (not sure how many million polygons it is, but at least one), and have similar specs to you Joopson. As Bek said, loading can take a bit of time, but once it's loaded things run pretty smooth…