What resolution will you be playing at and are you a heave gamer? Meaning what games are you in to?
You might need to update that BIOS for the D0 to work, have you checked in the ASUS forums to make sure? I would or even give ASUS a call directly to verify if flashing will be necessary.
Oh and SLI GTX260 will beat GTX285 hands down. SLI has come a long way and the 200 series cards have really shown that.
The reason I ask what resolution you will be playing at is if you will be running 1920X1200 and higher you will benefit a lot more from SLI if lower the GTX285 would be the choice for me.
Just about all games even if not enhanced for SLI will take advantage of dual or tri card setups. ATI CrossfireX isn't quite up there as GTX200 cards in TRI-SLI though.