Hi! Sorry for the late reply. I was little bit busy with work, so couldnt follow up on the thread. Finally lets get back to the basics, looking what would ultimately a gamer want?
If he is not a professional gamer then how much time would he spend on his PC? What is he actually looking from his headsets. Please correct me if I am not added more factors. Please do consider these factors.
How much performance expects from his video processor (indicating where does he lean more towards).
What is the kind of the Audio Card he is using. (what does he think about the sound/music in a gaming machine)
Is he a professional gamer if yes how long he sits on the platform... and what kind of games (how much comfort important to him. Different games have different bullet sound synergy for example a cross bow fired on a strategy game sounds different from 1 Vs 1 Encounter games. )
Environment he is using in machine in... bed room, class room, gamin arena, outdoors etc (will call for isolation, and sonic disturbance etc)
Temperatures & humidity of the environment. (headphones accumulate lot of sweat, they can start smelling).
Portability. (If he is professional gamer).
Most of the gaming doesnt require micro detailing. However sound fatigue is a sure factor if he intends to play for long hours. If you are looking to hear mouse mimic like a lions growl, then of course you are not looking for accurate balanced sound!
HD800 is not a good gaming headphone, why? for most of the reasons above and the chances are if someone is a professional gamer, he is likely to spend more money in the GPU. Top end sound cards do not reach anywhere close to top end Video Cards when it comes to prices. Also it is prohibitively expensive. At close to 80,000 INR for the headphones with the paraphernalia will cost you more than your car. On top of that, it would be rendering music, which was not meant to be audiophile quality!
HD555 was good till the time there was no option available, not anymore now. I get lot of mails from people asking suggestions for an upgrade from HD555.
One thing that I also must mention here. Most gamers as they grow in age tend, to lean towards music and good SQ. You should be able to get yourself a good gaming headphone, if you have all the above in mind. M50 has some good potential for a great all rounder. It is a very good candidate indeed!
Disclaimer: I am an Audio-Technica distributor. M50 is a very popular Model from Audio Technica.