I think you'll find the SE535 Ltd Ed fixes some of the short comings of the standard 535. Better top end, and slightly better bass extension. I just wish they had a little more bass impact. Bass texture is good though.
Still think they are overpriced for what they are though (although saying that ... I have no intention of selling mine ..... still love them).
The measurements (and my ears for that matter) show that the bass is linear flat down to 20Hz.
I've included the LCD-2s; headphones that no one has accused of having too little bass . Is the treble rolled off on the SE535s? It is so for most IEMs IME, but any more and I'd find them too bright.