Those of us who use IP softphone or voice-over-IM services have a component-related decision to make that is kind of unglamorous - but necessary.
What about the headset/mic?
You have lots of choices.
If you are really looking to economize, you can buy one of those economical models, like the $39.99 Logitech Stereo USB Headset 200 that I use. Not especially rugged or flexible, but works well for butt-in-chair, stationary VoIP.
Similar products include the Sennheiser PC150 Noise Cancelling Headset/Microphone, listed at $69.99, and the Plantronics Audio 90 Multimedia Stereo PC Headset, which rings up at around $34.95. If you are planning to use a PC headset for gaming and music as well as VoIP, the Sennheiser has its loyal cadre of fans.
The problem I've had with my headset is the fact that the cable is fragile. More than one headset-mic combohas been trashed by my bobbing and weaving head (too much coffee while working and wine while listening to those new-age MP3s).
With my record of headset carnage I gotta tell ya, wireless headset-mics are really starting to sound interesting. In fact, justgot an email pitch for the $69.99 PhoneRanger 2.0. I'll follow up and report.
What headset-PC mic combo are you using? While feedback is not welcome thru your headset, it sure would be via TalkBack.