I'm really only a student but I'll tell ya what I think on the subject. First of all, C Tenors and C Sopranos have been out of production for awhile now, so don't expect getting a new one. Second, key of E is 4 sharps, which is hell on any sax. That would transpose to key of Gb/F# on a Bb instrument (6 sharps or six flats). On an Eb instrument it would transpose to the key of Db/C# (5 flats or 7 sharps (YAY!)) So if you wanna stay on Bb Tenor go on ahead and kill yourself w/confusion. Or forage desperately for a C Tenor or Soprano (OR BASS!) and lighten the load. Believe me, even though I've only played for about 5 years, I KNOW WHAT I'M TALKING ABOUT!!!