Your final temperature will depend on how much you plan to overclock your processor and the ambient temperature of the room where your computer is located. A 3x120 radiator is more than enough radiator for any modern commodity processor currently on the market. But, since you are adding the 5770 cards into the loop, you may want to go for a 4x120 or 2 2x120 radiators. The nice thing about water cooling is that you can always add more cooling to your loop if you are not satisfied with the final equalized temperature of your loop. Just be aware that more radiator in your loop adds impingement, and your pump has to work that much harder to keep the fluid in motion.