single channel and dual channel aren't physically different types of ram
single channel is just that, one stick of ram in one slot. dual channel, on the other hand, is two sticks of ram in two physical slots, and it can utilize both of them in tandem to give increased performance. just make sure that the sticks of ram you get are good quality and the same kind, ie, don't mix a kingston stick with a corsair stick.
usually, dual channel boards are laid out like this:
-----------------(bank 0)
-----------------(bank 1)
-----------------(bank 2)
a stick of ram in banks 0, and 1 or 2, would result in dual channel mode. a stick in all 3 banks would give dual channel mode, but for best performance, banks 1 and 2 should equal bank 0, ie, 512 in bank 0 and 256 in banks 1 and 2.
bank 1 and 2, without anything in bank 0, would be single channel. hopefully that helps
, that's the way it works on nforce2 mobo's, i assume it's the same way for granite bay boards by intel, but i'm not positive.