I'm thinking of getting an Bulldozer proc machine, is there a ‘perfect’ graphics card for Houdini - I got a radeon in my current machine - the only card not approved for houdini - don't want to do that again. Price around $250-$500

In that price range, you can get the Quadro K2000, K600 or the AMD FirePro W5000. I'd probaby go with the K2000.

There is also the alternative of using a high end gaming card, such as the GEForce 680 or AMD Radeon 7970, though that has some driver disadvantages (as it seems you've previously encountered).

I use a 7950 3GB , seems to be running just fine. If you were not gonna go a consumer card, I think it should be a firepro, you will get better performance than nvidias for opengl.