Check out this article for a thorough and slightly gushy appraisal of the Boston Acoustics Sound Group II option for the 300.
I have it in my own SilverC, and can add my own endorsement (for what its worth) to why I think it's worth the extra $ to get premium sound.
I'm no where near to being a sound snob, but I do have a trained musical ear, so I know what sounds good to me, and having played in an orchestra I know when things are out of balance. I can say that SndGrp II does a great job of reproducing a very full sound, at both low and high volumes.
But, I'll leave the gushing to the guy in the article.
