Yes, the issue with USB headsets is that they use a built in DAC. This DAC bypasses any audio processing that you have on the PC. Thus, giving you sh** audio quality. The most popular entry level, audiophile headphones are the following.
All of the proceeding headphones will give you a much better audio experience than anything with an attached mic. Your best bet would be to purchase one of the proceeding along with a
mic. The Zalman can be head for as little as $5 when it is on sale.
Like I said earlier in the thread. I am also selling my set of Audio Technica A700's in "Like New" condition for $85 shipped. If your interested, shoot me a PM.
As for the sound card, I would suggest the Asus Xonar STX. The STX is a premiere headphone card because of its built in headphone pre-amp. Its on the upper end of your budget, however, it will give you plenty of room to grow your audio gear without the need to purchase a new source.