So basically, it's designed to give Quad-SLI on R3E - For this you need 2 x NF200 chips, due to the Nvidia design. - Xpander adds 2 x NF200 and 4 x PCIe x16 slots to give you this.
Xpander will be installed on the 1st and 3rd slots of the board.
The reason for this design, in my opinion, is that the NF200 chip can actually decreases graphics performance by approx 1.5% - Something you can't really allow on a board designed for breaking world records.
In the case of NF200, X16+x16+x16 is SLOWER than X16+x8+x8
(HardOCP did some research on this, if you're interested)
http://hardocp.com/article.html?art=MTYwNiwsLGhlbnRodXNpYXN0
So in the case of the board, the R3E outperforms a certain competitors board by approx 2% with 4 way CrossfireX 5870s. (Showing that if the design is right....Quad x8 > Quad x16)
When we look at Quad SLI figures themselves, the performance difference is approx 1.2% with 4 x GTX 480 (R3E with Xpander vs other)
In my opinion, the reason for the Xpander, instead of an onboard solution is quite self explanatory....
4-Way SLI is not for everyone, in fact, less than 1% of users use it.....NF200's are expensive, hot and are 6w of power each....If you dont *need* Quad SLI, they're just a bad addition for you, in terms of additional cost to the board. - Basically, you decide how your money is spent - Not the motherboard manufacturer.
(Note, you'd need 2 x PSU to run 4 x GTX 480 in Quad SLI anyway....) So when it comes down to the target audience of the board....you have the option of adding Xpander, if you really must have Quad SLI. It'll be a struggle to fit in a chassis, that's a fact...but anyone who is running 4 x GTX 480's isn't going to be doing so in a case.....unless it's a custom build (Can you imagine the heat of 4 x GTX 480 + 2 x PSUs!??!)
