That pump is WAAAAAAAAAY overpriced and unnecessary.
2 MCP35x's in serial would serve you way better. Or you can get the double top for the MCP355 which would be nearly the same (no PWM and maybe slightly louder which can be handled with getting a foam pad for it).
So you think I should add more pumps to get a flow rate of at least 1GPM ? Or do you mean to say that 2 MCP35x are better than 2 PMP-450S at 24v ?