Re: Gaming rig £650
120mm fan sticks onto the side of the thermalright. You need it so that your CPU doesn't fry. If you aren't going to OC much/at all then the stock HS/F will work but you need aftermarket (ie seperate ones you buy) for cooling OC'd chips.
If your worried about size pickup a Tuniq Tower 120 instead, slightly smaller, slightly less performance, but more bang-for-buck as it comes with a fan inside.