Asus p5k-e vs. Asus p5e

Asus p5e
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131219

Asus p5k-e
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131196


Of the two boards above, the feature I really am interested in is the dual pci 16x slots.

If I'm going for MAX performance, is the 4x PCI express in the p5k-e going to be a bottleneck for a crossfire setup? I'm debating whether the $100 is going to be a significant increase or not.



Hopefully I'm comparing two similar boards together, although its been so long since I built a machine I feel like I'm starting from the beginning again heh...



Thanks!