M Audio with enhanced bass

I ordered my 2008 M5 with the Enhanced Premium Sound option (also know as M Audio with enhanced bass). In the audio settings "surround sound" menu, instead of the L7 off/concert hall/theater options, you get 2 options: Stereo and Surround.

I cannot detect any audible difference between the two. Have tried different styles of music, different audio sources (radio, iPod, CD). In all cases, I can't hear any difference between the 2 settings. Anybody else have a similar/different experience? Is my "spatial sound effect" ('08 owners manual, pg 150) busted?

The sound system is fabulous, by the way -- doesn't really need any help - it kicks butt. Just seems like choosing between the 2 options ought to produce some sort of audible difference, no?

I have found the same problem. You cannot seem to select either and there appears no difference. Nor do you have a Logic 7 adjustment as I had on my 06 750i.... if you find an answer, please post or email, thanks.