Microphone suggestions?

So as a few people may know, i've been doing video reviews for games (Archive here, YouTube Playlist here), and one of the biggest criticisms seems to be the quality of my voice.

So far i've just been using an Xbox 360 headset, which I plug in to a wired Xbox 360 controller which is plugged in to a USB Port. You can hear what i'm saying but the quality isn't exactly great.

At the time that I decided to do these I didn't know if people would like them or not, but I generally seem to be getting positive feedback, and I enjoy making them, so I figure i'd be willing to spend some cash on a Microphone that provides higher quality audio.

I don't really have a set budget, but i'd rather not stretch past £100. My preferred form factor is a headset because it's simple to wear and doesn't take up too much desk space (Which is pretty cluttered right now).

I'm not too fussy on the connections, USB is fine but I also have a Sound Card with an Audio In socket so either should be fine. An example of what the mic sounds like would be nice as well, but I expect that i'd be able to find that myself if you're short on time.

So, any ideas?

Try having a look at this, it's what I mentioned on Twitter,
http://www.youtube.com/watch?v=EhRWs9XhR9g

Hmm, the problem with those are the form factors, I would prefer a headset because it's easier to wear, and doesn't take up much space.

After a lot of searching around, I managed to find one of these, and I even managed to find an audio sample of it here (Thanks to Sieabah L Park on the Machinima.com forums for providing a sample).

I'm tempted to go with this. I'll be shopping around to see if I can find it cheaper, but unless anyone has any other suggestions, this is what i'll most likely be going with.