Whatever you've been reading is wrong then - firstly, in the whole "newer is better you need more "tech" to be good" mythos (it's bunk with speakers - not much has changed since the 1940s), and secondly in the criticisms of Koss. The DJ100 are a fantastic candidate for what you want, and do not require an amplifier. None of the cans I suggested are boomy, per request. I couldn't stand the M50 either (I really think we probably have similar tastes - hence why I'm steering you away from extremely cold cans; I kind of "get" what you're looking for, but analytical, detailed, and natural does not have to mean cold, and cold is very fatiguing over time).
The A900X are also a fine choice, assuming they will fit your head. I think you'd be happy with either honestly. As far as the pricing, I've seen them between $220 and $299 at Best Buy, it seems seasonal.
The DJ100 seems good, but the coiled cable is a major con :E
I own both the Shure SRH940 and the AKG K550. The AKG has a wider soundstage but it almost sounds like it's less cohesive than the 940s. In my opinion, the Shure is more full-bodied sounding (maybe because the bass seems a touch more prominent) and makes nuances stick out more than the AKG. That's not to say that the K550 isn't detailed; it is, but it's a little more subtle. At times the wide soundstage of the K550 sounds a little strange with music, but if you want it for gaming, it's a top choice in terms of soundstage width from a closed headphone.
There are issues with both headphones though. As mentioned before, the K550 can be a little fickle in terms of fit. If you have a smaller sized head, it may not seal properly. The SRH940, on the other hand, doesn't feel like it's constructed all that well and there have been reports of the headband cracking. However, I'm sure if you don't abuse the headphones then it shouldn't be a problem. Mine are still fine, but it's just something that's on my mind every time I put it on and take it off.
Which one has better isolation in your opinion?