Graphics Cards that have SDI outs I am looking for a medium to high end graphics card that has SDI outputs. I have a home studio with a SDI matrix switch and I want to hook my Gaming Computer into this rig. I am planning on doing some gaming livestreams, and I want to use my studio m/e switch to control the stream. 

My other idea was to use some DVI to SDI converter, but since I have multiple monitors, it would probably be cheaper to replace my graphics cards
You are best off to convert from a supported format (DVI, HDMI, maybe even DisplayPort) to SDI.  SDI cards are not designed for gaming, they are designed for workstations and video.  You aren't going to get a good quality gaming graphics card with SDI outputs.