Are size, weight, battery life, etc. a consideration? If not, the Sager 9262 looks about as beefy as they come. 17" WUXGA display, dual GeForce 9800 GTX video cards (2GB total video memory), Quad core Q9650 cpu, 8GB of RAM...oh man I think I need to change my shorts.
If you're wondering about Sager's reputation for quality, check out the Sager section of these forums. I've had a 3790 for 5 years now, and the thing still kicks a$$. It's had a rough life, too. I'm now looking at the 5797 or the 9262, only because it's past time to upgrade. At the risk of sounding like a fanboy, I'm never going to contribute to any of the big companies' marketing budgets again.
Edit - I'm leaning more towards the 5797 now... http://www.pctorque.com/sager-5797-gaming-computers.php