There doesn't appear to be a comments thread for this article. Was going to ask if getting 3 single 4GB sticks would be ok, because they are not a matched set.
I've never had any problems buying non matched ram, even when overclocking. In fact i've just had to RMA the only matched ram i've ever bought because one of the sticks wouldn't run at the 1600MHz it was advertised to. If all the ram is capable of running the same speeds at the same timings, they should work well together in dual or triple modes in most motherboards.