Out of interest, why is 17" the requirement? While there are laptops that have screens that size, they're not as portable as one might think. Laptops with screens that size tend to be used by video editors, photographers, anything that involves manipulating photos and videos really, so a powerful graphics card is pretty much part and parcel of that.
I used to have a 17" PowerBook years ago and I can tell you, if you're wanting portability then a 17" machine is not it. Machines of these size tend to be used in the field when needed, so it's not typically expected you'll be carrying one around day to day–they're more a "need to head to a shoot, take the 17" and put it in the truck so I can edit video while we work" type of deals.
More importantly, you'll find that many places where you'd normally be able to use a laptop are no longer an option, simply because of the gargantuan machine you're carrying (coffee shops, airplanes - many places you would expect to use a laptop tend to be uncertainties with a 17" laptop). If you're going to be carrying this around for any length of time then your back is also going to let you know just how painful this is.
As pointed out on the thread, the rise of 15" hi-res screens provides many of the benefits of the real estate of the 17" without the drawback of the extra bulk - provided you're eyesight is pretty good.