I have switched out headphones a few times, and as yet I have no recommendation for a good one, only a recommendation that getting a good one first time will save you money. I have had:
Logitech stand alone microphone £10ish - too much feedback (not as good as headsets).
Logitech Bluetooth mobile phone headset thingy with Bluetooth USB dongle £30ish - poor sound quality and uncomfortable ear piece which eventually broke.
XBox 360 headset which plugs into XBox wireless controllers £15ish - the controllers automatically switch themselves off if you're not using them, so this is no use when I am playing with keyboard/mouse.
Creative Gaming Headset HS-450 £30ish - find it uncomfortable to wear for long periods of time. Ok for a couple of hours, but not for an whole lan.