Building PC's is like modding cars Lee - if you spec/build you can have it they way you want it....

Most times it does work out cheaper than just buying a system then adding a few bits to it, or changing a few bits....

I am building one for myself, cos a) I think it will be cheaper and b) I am too skint to buy one

But to replace the main downstairs family PC it was just easier to buy one (bought a new Dell system) as it had pretty much all the requirements needed (had to settle for Intel Celeron instead of P4 tho) and it was a lot less fooking around (as it is family PC I just needed something simple and easy to use with minimal hassle...