Here's my 2 cents: you can obtain decent audio quality with what you already have.

I use something like this:

Mine looks even crappier. You can use the headset mic, provided yours doesn't pick up too much breathing, I used to hate mine for that, it was too sensitive.

Next, the audio level in your pc's mixer. What OS are you using? Depending on that, the settings might change a bit, but basically you wanna make sure your mic has preamp on it (find a level that won't bring too much noise in) and after that you set the rec fader to a point before it goes into red, average minus 5 db. It's supposed to go to red only when you tap it.

Finally, record your audio. Do you use Audacity? You don't need much else. What you wanna do after you record, is normalize it and apply dynamic compression. The built in compression effect is good enough.

I'm gonna make a tutorial for this last section ASAP.