I'd go with the single 5850.
Here's my philosophy: Always pick a fast single card solution over a slightly faster multi-card solution. Remember that not all games are going to support multi-card setups, but pretty much every game is going to rock on a fast single card rig. Also, if you get the single card rig, there's always the option of adding a second one later, which gives you a value advantage over getting a multi-card setup from the beginning.
This guy know his stuff. I couldn't say it any better myself?I'd go with the single 5850.
Here's my philosophy: Always pick a fast single card solution over a slightly faster multi-card solution. Remember that not all games are going to support multi-card setups, but pretty much every game is going to rock on a fast single card rig. Also, if you get the single card rig, there's always the option of adding a second one later, which gives you a value advantage over getting a multi-card setup from the beginning.