I have been playing alto saxophone for about 5 years now, and I am going into my freshman year. My current saxophone is a beginner Selmer AS300, and I bought it used. I have learned and practiced a lot using this saxophone, but I feel that it is time to upgrade. I have already upgraded my mouthpiece to a Vandoren V16 and I currently use Vandoren 2 1/2 reeds. However, I think that my sound on the Selmer is not the best that it could be, especially since it squeaks whenever I change from a high note to a low note. It is almost impossible to play high E or high F, and the overall tone quality is not the best. I was wondering if I should upgrade my alto saxophone... and if so, how should I upgrade it? Should I upgrade to intermediate or professional, or should I stick my current saxophone? Should I buy used or new? Any other input is certainly welcome.