You missed an awesome deal last week. Amazon had a golden deal (one-day) sale on a Harman Kardon CL Precision headphones for only $64.99. Retail price is $250. (I snagged one. ^_^)
Anyway, as of the time of this post, the best sub-$100 (by Amazon pricing) headphones in my honest opinion is the
Gemini DJ HSR-1000. It's $80. It has great sound profiles and a very sturdy quality construction, unlike most headphones that are made of cheap plastic. It is also very comfortable.
The modmic would also be my suggestion for a mic. It's pretty much the only mic that i recommend using. The Zalman mic is cheap and cheap for a reason. It has terrible noise cancelling. Any noise whatsoever, like fiddling with the cable of the headphones (vibrations), scuffling of the shirt, computer / AC fans, etc are all picked up by that mic. It really picks up a lot of high frequency sounds. It makes it very unpleasant for the user on the other end who has to hear all that annoying ruckus.