I was going to buy an Azumi 2000 with 958 silver but I was also thinking of a Di Medici or Amadeus with gold riser, What's better

Which ever one plays best for you is the one that is better. There is no definitive "best" flute, as every player is different, and needs a different flute for the best possible match. Make sure you play test these all against each other (having them all at once is best, but if that can't be done, at least take thorough notes on what you do and do not like about each flute), and choose the one you like best. Material may not even make a difference. Some people swear gold sounds darker, but just as many hear no difference at all, so don't go in thinking about the material...Go in looking for the best possible flute for YOU.

I agree with flutist06. I personally prefer the Azumi.

a gold riser won't make you sound better, it will make a good player sound better/different and allow for more color.

Practice a lot, make your current flute sound great, then worry about what riser to get...