GEM has been running on Intel since the day after the announcement in 2005. You can find binaries here:

http://puredata.org/community/projects/software/gem/releases/0.91

Also, the Pd-Extended releases, including the auto-builds, for Intel will have GEM.

pix_movie directly uploads the image for texturing. Use pix_film followed by and pix_ processing you want and then pix_texture to upload the image to the graphics card.

PCI based capture cards using the BT 848 or 878 chips are well supported. They should have low CPU load with 640x480 capture.

pixelTango uses GEM. You can post the crashlogs to the pd list and someone will have a look.

Video mixing can be done using the graphics card too. Try putting the alpha and colorRGB objects after pix_texture and before the rectangle object. The right outlet controls the alpha transparency of the Geo and also the texture mapped onto it.