How about checking "Skip EFB Access from CPU"? I didn't have any problems with that setting when playing SSBB. Also put the Texture Cache slide all the way to "Fast". I also checked "Disable Fog" but don't know if that has any real impact on the performance or lags.
Edit: And when talking about Audio the XAudio2 back end worked a whole lot better for me with SSBB.
Edit: And when talking about Audio the XAudio2 back end worked a whole lot better for me with SSBB.