The TDK IE800? Never tried it. The RHA is more bass-oriented than the S1 and has less presence in the upper midrange and a less bright tone. The upper mids/treble of the S1 are more like the GR07 (good energy, not very forgiving) than the MA750. Anyway, both good earphones, just very different flavors.
big help man , but have you heard klipsch imave x7i ?