I would think about it as simply 23 is a student intro horn. Allegro, 475 575 52 intermediate horns, 62 82z 875 pro horns. The main difference between the 23 and intermediate models is the 23 does not have the tilting left hand spatula, and the 23 has nickel plated keywork that is very hard but great for students who may bump or bruise their horn, The 52s and the like have evolved. I have had some 52s that did not have the tilting spatula, but the later models do. Intermediate models usually come with high f# which is not on the 23. The difference between the intermediate models and the pro models is in the manufacturing process, not so much as far as features. You can get an intermediate model with all the options you fins on a 62 or 82z, but they may be made of different alloys or build differently. The intermediate models and pro models have lacquered keywork, not nickel plated. The intermediate models will offer a better "feel" overall than the into model...also intermediate models have plastic pearls as opposed to the real MOP found on the pro models. Any used Yamaha is a sound investment as well, because they will keep their value....the Chinese and Taiwan horns are more difficult to judge as far as them keeping their value.