It has been proven many times that SLI doesn't improve performance. Why spend double the cash if you aren't getting double the performance? That leads to adding another one later on when it gets "cheaper".
If you are getting a venice (which I do insist you do), I have heard that that Asus board isn't that bad. The word out on the street seems to be that Asus boards aren't too great as of late, though I can't say that the A8N is a bad board.
I can say that there is better though. Assuming you aren't an overclocker, the MSI K8N Neo4 Platinum is a very solid board. The SLI version comes with more goodies. I own one, and I have had no problems with it. The only downside could be overclocking, but DFI would be your choice should that be the case.