Why do you think the msi cools better? You are circulating hot air within the case. I would go with a stock cooler as they are quite sufficient for your needs. I second the vote for xfx for their superior warranty and evga would be second choice.
OpenGL is a competing API with DirectX3D. It allows programmers to more easily write programs using 3D and 2D graphics, just like DirectX. OpenGL is used more widely in 3D CAD programs while DirectX is used more widely in games.