Those radiators are really nice, even only one should perform quite well with 4 minions but I wouldn't use that pump. If you want to save more or anyone else is building a watercooling, a car heater radiator performs just as well as the most expensive computer radiators.

A koi pond pump would beat the crap out of it for about the same price. Just one of those pumps could service 30 minions in a properly designed setup.

I am developing a dual purpose phase change evaporator / waterblock and if you are interested I could hook you up with a prototype.
The current one is underperforming in the flow ressistance tests with water but I have narrowed down the problem and I am working on a solution.

I hope to reach my performance targets soon but meeting the needs of phasechange, watercooling and having a cheap and easy to assemble design is hard.

I think that watercooling is quite practical and a good investment due to the reuse factor, I have been using the same pump and radiator since year 2000 and even my original aluminium waterblock would have suficed with reduced performance but stil better than air.
In a crowded datacenter it would make even more sense as you could reduce the air conditioning bill by a lot if you place the radiator outside and you could use car or truck radiators with a nice and big pump (or several in parallel to increase the reliability).  It can also be cheap, as I have said the pumps and radiators can be shared and cheaper that those sold by computer companies and if you diy the waterblocks it is not expensive at all.