I dont know about the A8N. but i've heard its very good.. its the board my friend chose over anything else for his SLi setup...
however, my Asus experience hasn't been great. I burnt my 478 p4p800e deluxe from oveclocking but got it replaced so its all good.. But, its got some great features on it.
DFi are known for their overclockability and overall performance, although I'd say the Asus would be more reliable assuming you wont be overclockin ur FSB.
If it was me, I would go with the DFI completely out of word of mouth/reputation. but just go with whatever ur budget alows
Sig reinstated. SigSanta