PapaFunkyFunk

Thanks everyone gonna go with either the Fiio E10 or the O2 and hopefully be able to hear people sneaking up behind me. 
 
Great comments. Cheers. 

DT 990 is good but you'll need an amp. Don't need a DAC, it won't be much of an improvement.
 
Fiio E10 or the objective2 will work.
 
AD700x is a good headphone, and you don't need an amp/DAC. Just look for an open headphone.
 
No sound cards, and surround software normally make a good headphone sound bad.

Much win. Such mission accomplished. wow.

Most games have a built in headphone option in the audio menu. No surround software is needed.
For positioning you'll need an open headphone. Some closed headphones are okay with this but most under $200 are not.

You'd definitely want amplification for that DT 990.
 
The big problem with soundcards is the output impedance causes boomy bass and high frequency roll off for low impedance headphones, which the DT 990 would be immune to. However, if you want to try other headphones in the future, most will be low impedance and thus suffer from impedance mismatching with a soundcard. All that doesn't even go into those possible driver issues you've mentioned.
 
The reason we recommend the FiiO E10 instead of cheap soundcards is because of that high output impedance of the soundcards. The reason we recommend an O2 instead of an expensive soundcard is because it's better than everything on the market under $1000. You can get an O2 amp without the ODAC cheaper than a "top tier" soundcard like the STX or Phoebus, and it'll be compatible with more headphones.