Use the DVI ports. This way you have four available across 2 cards. Just about every monitor with an HDMI port also has a DVI port. This is actually the only way to setup 3D/2D Vision Surround on the Nvidia cards:http://nvidia.custhelp.com/app/answers/detail/a_id/2667
You won't get the result your looking for through an HDMI splitter as it will only duplicate a screen image from one to the other.
You're trying to run 3 screens in 3D or 2D surround which expands the video to all 3 screens. So an HDMI splitter is not the choice for you.