Another data point to consider:
http://www.audialonline.com/online-topics/psu-transformers-ei-vs-toroidal-and-more/
Note the graph showing the bandwidths of the various transformers tested and the discussion that follows.
http://www.audialonline.com/online-topics/psu-transformers-ei-vs-toroidal-and-more/
Note the graph showing the bandwidths of the various transformers tested and the discussion that follows.