The fastest ram is the kingston Hyper-X 2133mhz, it's a bit overkill and Clevo's don't like it, but I believe MSI and alienware can run 2 sticks at stock speeds, but struggle a little with 4.
Dual channel does interleave data like a hard drive raid array, you can stack mutliple dimms on each channel, but you only get a bandwidth increase equal to the number of channels the chipset supports.
For example: Z77 = 2, X59 = 3, X79 = 4.
You need to run 1 and 3 or 2 and 4 to get dual channel, though they are usually paired like that in notebooks so that 1 and 3 (as the chipset) are together.