[theaudiologist]

I might get a pair of audio-technika ath-m40x but is it enough to tell the difference between 16/44 and 24/96. How good should my headphones be to do so?

 

[Monsterzero]

You need to consider what DAC and amp youre using as well before deciding what headphone will/wont make a difference

 

[Me x3]

HD800 and SR-009 are your best bets, but even then best chances are you won't be able to tell 16/44 and 24/96 apart.

 

[PurpleAngel]

  I might get a pair of Audio-Technica ath-m40x but is it enough to tell the difference between 16/44 and 24/96. How good should my headphones be to do so?

 
Do you even have any music sources that are 24/96?
CD-audio is only 16-bit/44.1K
 
If the ATH-M40x are what your willing to budget for.
Not sure what 16/44 verses 24/96 have anything to do with your choice (or budget) for headphones.

 

[tomb]

  You need to consider what DAC and amp youre using as well before deciding what headphone will/wont make a difference

^ This ... absolutely.