My Definition, in depth
Event at high end, assuming blu-ray, a 20" screen, core i7, 6GB RAM, 1TB drive, blu ray and a HD5770 gaming graphics card, you're only looking at about 900 quid for a Pc and monitor, and that from 10 minutes' work on ebuyer. As you bought a mac and a laptop at that, you obviously don't need the graphics to be too great, so knock another 100 off that, maybe 130 iif you can manage with onboard graphics. The graphics card means your PSU requirements go down so that's another 20 quid or so we can ditch, and you only got 4GB RAM with your mac, so at least another 50 there.
If you're going to buy Apple, it will cost you about a thousand pounds. If you buy anything else, it really shouldn't.