Now that just sounds daft when you have a rig with the specs like yours, I mean THREE graphics cards!! What makes you stick to the laptop?
Me personally use my PS3, otherwise I only have my MB Pro in my sig, but I've exclusively had an MB Pro for 3 or 4 years now. I have gone through bootcamp to play Crysis and HL2. I got a few PC games but not bothered about them and finished Crysis although I have attempted to try and play it under a virtual window or Crossover Games with no luck. So when Steam was launched, I didn't bother with anything else on my new machine, Steam went straight on as soon as i got it and that will be staying on.
So my MB Pro and Steam and my PS3 plus my PSP and iPhone are MORE then enough of a gaming fix for me.
But with the performance my Mac has and with a commitment from Valve and Apple to make better support and drivers for games performance I think my lil machine will keep me going for a long time.
I could happily and easily build myself a kick ass rig, but I don't want to. I just prefer a laptop for my PC needs these day's rather then multi core, screen, GPU machines with pretty lights.