actually, the route that you have drawn up there looks like a very bad idea, very inefficient. mainly because you sort of have two loops there. there's no guarantee that the water the comes out of the loop with the blocks in it is going to get drawn into the radiator, and likewise, the cooler water out of the rad could be sucked directly back in instead of going to the blocks like it should. and like was said previously, if you're gonna go to the trouble of having two pumps, why not make it redundant? you might as well get something out of it. also, you're cutting way back on the effeciency of the rad (you get the most heat transfer out of the coolant when you have the highest temp difference between the coolant and in this case, the surrounding air). you're gonna be sending a lot of heat back through the cooling loop this way, and your temps are gonna suffer for it.
check
THIS thread out, very similar topic.