I have had 3 headphones so far, the ath-m50, the dt-1350, the fidelio l1. Those were good enough for me before I auditioned the t51i yesterday. I was very impressed by the t51i that i now consider them a solid improvement over the other three ones. What i liked about them is that they have bigger and warm sound, excellent vocal presentation, and an overall smooth and clear sound. I kind of wished it had a bit more treble, but its treble is no deal breaker. Now i am thinking of going even bigger and better. I want a headphones that is an improvement or an upgarde in sound quality to the t51i, yet maintain the same fun sound signature, preferably with a bit more treble presence. I was thinking of the shure 1540. Will the 1540 fit the bill? Are they an upgrade in sound to the t51i? I am open to other suggestions. Thank you!