I thought I addressed the mac-gaming thing, however, here we go again:
To game on a Mac decently (every mac game I've ever seen run is a slideshow, literally), you need to install windows, which completely folds the usefulness of the Mac. Any PC laptop will give you better hardware for the money with a legit copy of Windows already installed.
As far as DJing goes, I've never seen a professional DJ use a mac (except for those I've seen at this university, which are far from "professional"). Most use a PC and a program called PCDJ-FX. It only runs on XP as far as I know, though. I work for a sound productions company, so I've seen a lot of concerts, dances, weddings, parties, on and on.
All in all, I would not recommend getting a mac if you're going to game. The cost is way too high and the hardware you get for it is midrange. You can get much beastlier hardware for the same price elsewhere.
EDIT: oh, and I'd swear by my Sager.