I'd agree with Tom on these- Though can't comment on the Graftonite as i've never played one. I'd also add ebonite Yanagisawas & BARIs- both ebonite and metal...1. Rico Graftonite - I have a B7 Soprano, best £15 I have ever spent. Lively without being in any way screechy.
2. Vandoren V16 6S HR - my main mouthpiece of choice. Lovely tone but with some edge.
3. Brancher J15 Metal - very close, again not in any way painful - the trouble I find with Soprano.
4. Berg Larsen Ebonite - as initially used by Jan Garbarek. Again lovely tone but not sock like. Used
Excellent advice - never realised they were so cheap. Ordered one from Trevor Jones so we'll see how that works out before I start looking at anything more exotic.Get a Graftonite at the very least (good range of choices available!) before shelling out the pennies
Since you are OK with a 7 on alto, i think you can go for at least a 7 or 7* on tenor. I switched from a 4C to an 8 without any difficulty. Somehow i feel that a wider tip mpc helps to play low notes (most will disagree however).