The gear in this topic is what I use.
http://videokarma.org/showthread.php?t=271494 The only downsides are panning is not perfectly smooth, action scenes with a lot of camera changes or motion can get choppy, and sometimes there artifacts from the down-convert, up-convert, down convert cycle... There may be better options.
Edit: setting the Extron to 480x640 output has eliminated all noticable artifacts and reduced motion glitches...shoulda done that from the start!