Hey, I was thinking about doing the same sort of water-network. I want to run it in parallel, but I've never seen a 3-way splitter before? I've seen the classic "Y" type 2way... What block are you planning on using to cool you're N-Bridge? ...Wait, I just got an idea, if you're pretty handy with soldering etc. you could make you're own 3 way splitting from copper tubing, which would add very minor to cooling. I've replaced the plastic head on my pump with a 3/4" copper in cap I drilled and soldered 1/2" nips to. I doubt it helps much, but you can feel the heat it conveys, so every little bit counts!
I'm running large 5/8" ID tubing and 1/2" nips... I need to get a higher pressured pump, but I just can't seen spending over $30 for a damn aquarium pump! Some people, I've notice'd are spending like $70+ for a pump?
Does anyone have any links or is selling a used pump for cheap? Good luck guy.