DAddario Woodwinds Alto Sax Select Jazz 5M

I would recommend you consider this as your first step up from a Yamaha 4C. I've had one for a number of years and used it a lot - until a couple of years ago!
Then I discovered other, better mouthpieces - WCW56, Rousseau 4R, Vandoren, Yamaha Custom and best of all, the Selmer S80 C*. Moral 1 - always try before you buy. Moral 2 - price is no indicator of how good a mouthpiece is. Moral 3 - it is the mouthpiece/reed combination that is really important to the sound and response. Try many different reeds to find compatibility with your mouthpiece.
I find the D'Addario can sound a little 'honky' compared to other mouthpieces.