Right now I'm using a Vincent Bach 12 and that has been a great mouthpiece for me, giving a large range and reasonable tone. But in my experience it sounds as if my tone is slightly lacking and my range reaches notes never seen in any of my music (including solo work), so I was thinking about finding a new mouthpiece that would improve my tone, even if I have to sacrifice range. I've been looking into getting a Bach 10 instead. What's your opinion on the Bach 10 and if what's your personal favorite mouthpiece for best tone quality?

EDIT: I actually have a 3, not a 12, oopsies.

Based on the size of what you are playing with no apparent problems on range, I don't know if it's really helpful to go to a smaller diameter. I would think it might be worth considering the Denis Wick mouthpieces. His heavytop is almost the same diameter and rim as what you are using. You can also go to the classic or paxman series. The big thing would be the deeper cup they have than what you are using now.

Alright thanks so much for the advice. I looked into it a little bit and yeah it seems like Denis Wick has the sizes I'm looking for. I'm undecided which one is better suited for me, a heavy top with a u shaped cup (5N) or a larger diameter but still V shaped cup (4N)

I would suggest you to go for Dennis Wick mouthpieces. Hope you find the one you are looking for.