I 2nd the Shure SRH840. Haven't tried the A, but I asked Shure themselves, and heres what they said: "Acoustically, they have a similar sonic signature to the original headphones with some improvements: lower total harmonic distortion characteristics and hand-sorted drivers with matched sensitivity to ensure clean, consistent and neutral audio reproduction. The biggest changes to the new ‘A’ models are improvements to the comfort, durability, weight and appearance."

Either way, I love the SRH840.