Go for the DIY version?
Must admit that im tempted by this...
I specced up the equivalent on ebuyer (was on the site at the time so thought id waste some time at work...) and it works out slightly cheaper than Dell...but whats new.
Overall a nice little rig in my opinion. The other XPS options are pretty sweet too, if youre looking for a nice gaming setup, though get a little more pricey!