Thanks for your response.
It does matter to me that the headphones are closed, as I plan on attending several LAN events in the future with my setup.
I can't have outside noise getting in the way.
Would that Sound Blaster Z be ideal for such low ohm headphones?
I'm basically looking for a setup similar to what LiamIV just described above.
I need highly competitive directional sound, but I'd like a rich full sound for when I'm relaxing and playing RPGs and such.
If you want the best of both, you're gonna need two headphones... Sorry to break it to ya.
The MA900 would be a great choice for relaxing with a full body, but for a closed can you'd probably be best served by something with a fair bit of treble sparkle (especially in a loud environ) and air, so a bit less bass (which closed headphones naturally/usually have more bass). I'm not quite sure which closed can to recommend, I haven't often been in that situation... from my experience though, if you really need to shut out the outside world and focus on the audio, nothing beats the abilities of an IEM. Joker has a huge thread of IEM reviews, so look there for one with good treble extension and pretty neutral bass (or see if you'd be allowed to EQ down the bass a bit). For a closed headphone,
I have a V-MODA M-100, which has actually a good sense of positional imaging IMO, but the bass is a little "fun" for competitive use, and long-term you need to give your ears a break. From what I read, the XL Earpads decrease the bass while increasing soundstage and comfort, so one day I'll probably pick a pair of those up, but keep in mind the M-100 is a $300 closed headphone.
When you go to these LAN events, are you bringing a desktop (m-atx sized?) with an available internal PCI express card slot, or a laptop? If you need a small, external, easy to transport surround processor and DAC, the Sound Blaster Omni may be a better choice for you.
I don't know what the Omni's output impedance is, since it's one of Creative's most recent products, but if you're ever worried about output impedance mismatch, pick up an external amp with low output Ohms, like the cheap FiiO E5 or a more expensive amp to match your headphones. Side note: the Sony MA900 has an impedance compensator, so that one doesn't need special consideration in that way.