I like the sound of my Beyer T70 (250-Ohm) and I bought them used for $310 (225 Euros) and I do like them, but I do not think anyone should pay more then $300 for them (new or used).
Thomann sells the AKG K550 for 177 Euros, so you might want to read the reviews on those.
The Audio Technica ATH-A900X do have a nice sound to them, I paid $256 (new), wish I had waited and just bought used ones for $180.
The SBZ (Sound Blaster Z) series is starting to appeal to me, the Zx seems a good value.
The SB ZxR is overpriced for what your looking for, it comes with an extra DAC for speaker surround sound, but as your using headphones, it not a good value for your use.
So the SBZx seems the better choice for you.
I do own the Asus Xonar Essence STX (with AD797BR op-amps), does a great job of driving my T70s (and other headphones).
A Fiio E12 might be a good choice for use with your Samsung Galaxy S3, or just a Fiio E11.