The loops, radiators and pumps really depend on the specific system setup you have and what components you want to water cool. Since you are doing a dual video card setup it can be a little tricky. I would say you might benefit from two radiators in order to keep the cooling at its maximum level. Something like the following would be okay. Reservoir to pump, pump to cpu, cpu to video card 1, video card 1 to radiator 1(dual fan if possible), radiator 1 to video card 2, video card 2 to north bridge, north bridge to radiator 2 (single fan is fine), radiator two to reservoir. Of course they sell coolers for your memory and hard drives, ect. Those I would put after the north bridge before the second radiator.
As far as which ones to use. Read as many reviews as you can for the products just like you were picking out any other PC part to get the best feel for which one you want. I always try to go by the products with the best reviews even over my brand preferences as it can save the heartache from a crappy product in the end.
Also here is some sites that will get you more information on setting up a water cooled system. Oh....HAVE FUN!!!!!!!
Get your facts first, then you can distort them as you please.