And just times it by 2. So you have 12 watts of of heat dump per pump. And this is back in 07. The pumps that your using now might even be more efficient. So I wouldnt worry about the heat a second pump would add to the system. Especially with that radiator. It wouldn't even raise the temp of the water if you ran both pumps and the radiator with fans.
Now as for doing two pumps for redundancy, it isnt a bad idea. If I had the ability to do it, I would, but I dont right now. So later on I will.
If you like the way the res looks, and you like the setup you have with those pump. Stick with it. If you do it, I would be jealous.