Hmm, just found this thread.
I didn't really read through it, just glanced.
A few words...
First, I would not go with any over-the-ear phones like Grados or Alessandros. They sound great but for gaming, the soundstage is never very accurate which is always priority number 1. Also, they're not sealed (which some people consider important for gaming). I would also stay away from headsets and 5.1 phones, they all generally suck.
I saw that some people recommended the K501. These are my current cans and they have beautiful musicality, but for gaming I don't really like them...the soundstage is very wide but it isn't very deep, thus making the front and back feel too linear while the right and left go out very far. It makes for a weird effect so I would avoid this...also, since they are discontinued I wouldn't bother trying to get one. Your uses wouldn't give its sound qualities justice.
Some of the best gaming phones lie within the Audio Technica line. The $100 A500 makes a great sealed, intro-to-audiophilism headphone with excellent imaging and soundstage, and they don't sound too shab for music either. This is the first phone people recommend for those who want a gaming can. I've owned a pair of AD700 (which is an acoustically open slight step up from the 500 line) and I couldn't ask for more as far as gaming is concerned. Since it looks like gaming is your number 1 priority, I would go for a pair of sealed audiotechnica's, which can be had for $100+ at audiocubes.com.
Other good options include Sennheiser HD555 and HD595 with good soundstage and decent imaging, but again they aren't sealed which can be problematic for lans and such. The DT770 is another option but I personally haven't heard it so I can't really add anything.
As for myself, I've got a DT880 sitting under the christmas tree that I can't wait to hear...
Good luck.