Get a 1333MHz CL9 kit, timings and frequency of the RAM has a very minimal impact on performance for Sandybridge. See here in regards to frequencies: http://techreport.com/articles.x/20377
Yes a 750w is more than capable of handling SLI GTX 560s and even SLI GTX 570s. There is probably better options than the TX750 though such as Antec Truepower New, Corsair TX v2, and XFX.
Without knowing the retailer / website you are purchasing from, it is hard to say if there is something better than the Zalman at that pricepoint.
What kind of features are you looking for in a motherboard? It'd probably be better to opt for a Gigabyte P67 UD3 or Asrock P67 Pro if you are just using this board as a placeholder.