SRH-840 vs AD900

I use my AD900's for gaming, and though I've never really needed such high precision for anything, I'd say they perform admirably.

If I'm listening to progressive music, I am always impressed. I like them for classic rock and what classical I have.

I can't comprae them to the Shure headphones, because I've never heard them. In comparison with my Grado SR225i headphones, they have better "clarity", "instrument seperation" and especially "soundstage".

The soundstage is really phenominal.

Both headphones are easy to drive so you don't need an amp with either.  In fact, the Shures will work very well unamped.  Both headphones offer outstanding sound quality with clarity and excellent detail retrieval, there are some key differences though.  With the open air(no sound isolation at all) design of the AD900 they have a larger sound stage than the SRH840, that(if you do a lot of competative gaming) will come in handy.  While the SRH840's soundstage is excellent for a closed back design, it does lack the size and depth of the AD900.  Though, you can chalk that up to more the fact the Shures are closed as opposed to open.  The SRH840 has a stronger and deeper bass response than the AD900 so it will handle your bass heavy genres better than the AD900.  Hmm, tough choice.  How about you flip a coin?

I would say that the Bass of the AD900 is a bit lacking if that's what your'e after. I'm not a huge fan of epic bass, so they suit me just fine, but if your'e a basshead, the AD900 is probably not for you. I'd say they have good-sounding bass, but what is there isn't very loud or overbearing. This may affect the sound of explosions in your games. You won't "feel" it as much.

edit: spelling

Also, some peolpe have reported fit issues with Audio Technica's wing design. I find them to be extremely comfortable, and have worn them for 14+ hours playing Oblivion.

The material used in the earpads and headband is synthetic leather.  Most heaphones use synthetic leather, it is rare to find one that uses genuine leather.  That is usually found in the more(more as in very) expensive models.  Some additional options:

Audio-Technica ATH-A900, AD1000

AKG K702

Beyerdynamic DT 880, DT 990

Denon AH-D2000

Sennheiser HD598, HD600

Well then, if you want to avoid getting an amp then this revised list of options are for you:

Beyerdynamic DT 440, DT 660, DT860

Denon AH-D1100

Grado SR80i, SR125i

Sennheiser HD558, HD598

Ultrasone HFi-580, HFi-780

All of the options here are quite efficient so they will work well with portable sources, laptops and PCs.

Yes, with the exception of the Grados, all of these options will excel at gaming.