When you have everything in series they all get the same flow - the first thing after the pump does not get a higher velocity. If the first one was getting more water than the second, where would the extra water go?
The water temperature across a component changes very little - on the order of a couple tenths of a degree. Will you be able to notice the tenth degree difference between having the rad before or after the CPU block?
Since you are using a waterblock with dual outlets, you should save yourself the flow restriction of the Ys: Pump->GPU->NB->CPU=>Rad->Pump
|