You don't HAVE to have triple channel RAM, but you should so you can take full advantage of the triple channel RAM controller on the CPU. Of course that's only true if the OP is using a 64-bit OS. What OS are you planning on using?
Win 7 ultimate 64 bit
well for the moment I'm going dual channel to balance cost
after a few months will add another 2gb stick.
But what about the mobo?