Well.. if $100 is your limit, I'd suggest a Turtle Beach Santa Cruz with Logitech Z-340 speakers. If you look around, you should be able to get both for at or less than $100 total. Newegg would get you close.
Edit: Newegg's total for the two comes to $108: Santa Cruz - $62 + free shipping; Z-340 - $36 + $10 shipping. If you can afford to wait a few weeks, chances are pretty good that some place will have rebates on them giving you a significantly better total.