Said it once, I'll say it again.

You could spend £1000 on a PC and a year down the line it'll be running at a snail's pace.
Spend £1000 on a mac, and you'll have a computer that will seem brand new for over three years. Mine still does, and I got it in Jan 2008. Although I'm getting a new macbook pro in a few months because I like the design over the plastic macbooks.