i didnt know about the modmic... that seems like it could be nice, but about 2 years ago i got a blue yeti,
i set the thing to only whats in front of it and adjust gain till i stop hearing the pc fans when i play a demanding game...
i can stand 10 feet away from the thing and it picks sound up better than any headset my brother ever use, and it sounds better than any "pro" quality headset thats under 300$. there may be better mics, but the versatility of the yeti, on mic gain and position controls FAR surpass anything else i have even had the chance to use or listen to for under 100$
as of right now you can get the blue yeti for 96$ new (black one) and 74$ used (sliver one) new is 109$ and as far as im concerned its money well spent.
also, a fiio dac amp is a FANTASTIC deal for driving headphones, my brother and me have about the same on board audio but he had the fiio i think 10, i go about straight form the pc, the onboard cant drive my headphones without pops and quality issues his drives them perfectly... though if that extra quality is worth the 70~$ is another question entirely...
small edit, i also for headphones recommend at least sennheiser hd 518 as it has a removeable cable and the price puts it VERY competitive with other headphones in the range, and with few exceptions is better than them... on a side note, i currently use hd 598's, and if you get a 558 you can mod them to be as good as the 598 but even unmodded, they are still great sounding headphones.