I think a few guys have done this. Here is a recent thread with some pics from Walked U's car with the resonator deleted and test pipe.
http://www.e90post.com/forums/showthread.php?t=67255
Removing the secondary cats and resonator shouldnt cause any CEL as these are after the 02 sensors. I have heard the sound, and it actually sounds pretty good with the stock mufflers. Maybe WalkedU can chime with a video clip.
