The E6550 has 65nm architecture.Why are you watercooling a 45nm CPU? IMO, it's not necessary.
In past years watercooling was needed to cool CPUs at high volts. With newer processors you'll kill your chip at much lower voltages. Before your CPU gets hot enough to really require WC, you've already killed your chip.
Oops! My mistake...The E6550 has 65nm architecture.
I'm not really in a position to give advice on water cooling though.
Since you have an antec 900, do you really need water cooling?
What temps are you getting?