Audity from VJA?
And no, you're best off putting that extra $100 into better headphones. Chances are anything that price is going to make the sound worse unless you can find something like the EMU 0404 USB for that cheap, and even then you'd be best off getting some better headphones (that aren't picky like the HD650). The ESW9 sounds great out of a lot of stuff including lower end sources. Pretty popular but some don't like it (see the DC meet impressions thread).