there is no such thing as single channel or dual channel ram... it all depends on whether your mobo can run ram in dual channel... if it can, then two identical sticks will run dual channel in the appropriate slots. Ram marketed as dual channel just means it has been tested together and runs in dual channel. however, if you are like me and think of this extra cost as a marketing ploy, just buy two "single channel" sticks that are the same and they will run as dual channel no problem!
Just make sure your mobo can do dual channel though, otherwise there is no point in even considering this!