Re: Is used studen alto saxophone from ebay better than my new one
Whether or not you should keep your current horn depends strictly on how well it works for you. You say you like it, so it seems that no problems have made themselves evident at your level of playing. But there are some quality control issues that are known to affect inexpensive Chinese saxophones regarding playing in tune, key fitting, alignment, correctly formed tone holes, durability, and so forth. I'm not saying that your horn has those problems, but you should have it inspected and play tested by a tech to see if there are any latent problems related to its build quality and playability. If there are, consider some good used student horns that are frequently on the market in your price range:
Selmer Bundy I (with the left side bell keys) Do not get a Bundy II (right side bell keys).
American made Conn Director "shooting star" Consider only the ones with "Elkhart, Indiana" or "USA" engraved on the bell. Avoid the ones made in Mexico.
Conn Pan American
All of those horns have older style keywork. If you want more modern keywork the Yamaha YAS-23 is a good option. They tend to cost a little more.
Consider only horns that are in good condition. If a student horn is in need of significant repairs, it could exceed the value of the horn. The buyer's guide on this site contains lots of useful tips for avoiding bad deals in used horns.
If it turns out that your new horn is worth keeping, save your money for the day when you get the horn you will truly want as a more advanced player.