Soldato
NF200 is just a context switcher hence why XDMA doesn't play nice with it - instead of having 2x true 16x ports you have 1x 16x split and it switches between them as needed/load balanced. So it can't truely talk from one device to the other in different sockets in the same clock cycle.
Its great for SLI however.
My new Board uses something similar called Plx Pex 8747 "Asus P8z77 WS" It runs superb with my cards. I honestly wouldn't know any different.