Looks beefy. Since your head is brobably not going to exceed 50cm, you'll get 500l/h on each block... That's enough for most cooling applications! I can't answer how quiet, energy effiecient, and reliable it is
One concern is your heatercore... 1/2 inch ID lines ain't gonna cut it... personally I would go with seperate pumps in order to avoid having GIANT diameter hoses...
(trust me, I am running a 1000l/h system on an Eheim1250, and my D-tek customs radiator is the bottleneck although i'm using 1/2 inch ID tubing... plus, managing the hoses is a giant headache!)