I think i'll just jump into this discussion.
As an user of A8N32, i have no complains over this board. It is a sheer engineering perfection as compared to the DFI board. However, when it comes to chosing the board, here's my oppinion.
OC:
Most people will go DFI all the way. However, the A8N32 offers a great range of OCing options, some of which I have yet to understand its functionality. DFI has MORE options, and i doubt there's many people that knows exactly how to tweak those little settings. For almost every1, the A8N32 will OC your CPU far enough for you to get phase-change cooling, and is easier (IMO) to clock.
I'll say they are on par, unless you have those ultra rams that take more than 3V, go for the DFI. Asus doesn't have enough RAM voltage fro those monsters.
Side note: I was told that by the engineers the 8 phase power will allow a more stable OC due to the fact that there's less oscillation in the power phase, and thus less fluctuation in supplied electric power. My Opty 165 is sitting on 2.56G @ stock volt.
Cooling:
Recently reviewed in my personal post, Stack Cool is absolutely outstanding. It does exactly what it's supposed to do, however! The X16 chipset consumes 20W more power both idle and load than the DFI, therefore INCREASING the heat that need to be dissipated. I am unsure whether stack cool will conpensate for this 20w of extra heat and still be able to help cooling the CPU...
DFI's north bridge can be easily replaced by a Zalman, but i know in a case without sufficient airflow, they can rocket up to 45C
SLI:
DFI is the clear winner, due to the fact that NO existing card/game can saturate the 8X PCIE lane, it is an overkill to have 32 total PCIE lane.
Upgradabilty:
A8N32 is clear winner, it takes 2 dual slot card (in my case 2 cards with Silencer) and still has room for a PCI sound card.
Price:
DFI is cheaper than ASUS
Decision is up to you
1st on my personal wish-list:
A8N-Sli-Delux!
8Phase + Stack cool + Nforce 4 Ultra chipset (no X16!!!) + 3~4 dynamic fan control connectors