The only issue I see with the P5N-D is that the PCI-E slots are only 1 PCI slot apart. Make sure your cooler will fit. Also know that there will be little ventilation in between the cards.
I'd also suggest looking at 650i and 680i motherboards. Because they have been "replaced" by Nvidia's 7xx series, they are often very cheap for the features they offer. 680i boards that used to be considered high end can now be had for around 150
or less. The 750i chipset is identical to the 650i except for having PCI-E 2.0 support.
Speaking of PCI-E 16 2.0, I consider it the same as Sata 3GBs. No GPU/HDD can respectively saturate PCI-E 1.0 or Sata 150. Both buses were made bigger just because they could be. Unless some new GPU can actually saturate PCI-E 1.0, PCI-E 2.0 is pure marketing.
Also note that in most cases, when using the PCI-E 16x slots with the P35 chipset, the second slot will only operate at 4x. I'm pretty sure that the upcomming P45 has native 8x, 8x Crossfire.