well to be honest a lot will depend upon the spec of your current machine, and what you intend to use the new one for.
If you are only going to use it for word processing, e-mail and web browsing, then do you really need the power of the all singing, all dancing, GTI TURBO version? Then again, if you are a serious gamer you will need all the above.
There are so many variables out there, mother board choice, on board sound/video (good for basic users), AMD/Intel chipset...the list is endless.....
For what its worth i just rebuilt for aprox £300 with some parts of my old machine (case, PSU, sound card.....)
I hope your hair is not on fire now
