So I'm watching the price of W700 units slipping to beneath a grand on eBay, and I just can't help but think that it would be so cool to have a 17 inch Thinkpad. On the other hand, a W520, with significantly better specifications can be had for not much more.

But it would be so cool to put a W520 board in a W700, if that's possible (we are talking a down the road upgrade, this is not something I would do all at once). I know HP uses the same form factor boards for at least some of their laptops, and just runs longer cables through the machine (dv6000/9000 come to mind). Or how like all T4X machines has the same basic board, and just the interposer card to make up the difference in width from 14 inches to 15 inches.

So, does the W700 use a unique board, or can a W520 board be used with the W700 plastics, LCD, etc.

Thanks for the help guys!

Not possible.
The W520 (W510 has similar or same board dimensions) and W700 have significantly different motherboards as illustrated by these (W700) photos (W510).

That said, though, there isn't a lot of difference between a W700 with a Q9000-series processor and a W520 with a 2720QM other than power consumption and heat, especially if you add an SSD to the mix. So if you want a W700, get a W700; you can upgrade parts later as you see fit. And besides- graphics in the W700 series are faster than those in the W520 series; though the Quadro 2000M series approaches the FX2800M in speed, you're looking to spend another 250 bucks on that upgrade. The Quadro 1000M doesn't come close.

Good to hear.

I have not stayed on top of Intel technology, most of my Intel machines are fielding Core 2 Duo or older. While I know that cutting edge Intel is better than that of AMD, I've never used a Core 2 Quad CPU. Do you have any idea how that would compare to say, the Phenom II's?