I look into places like
"Will it run?"
Also, I find certain connectors for liquid cooled systems to be lacking in the quality department for computers. So I'd consider some automotive accessory equivalents (they have to endure much more hostile environments and continue to be reliable for years, even decades). I always look at reviews of any product, especially harshest criticisms and more importantly failures.
I find few if any liquid coolers take laws of thermodynamics completely into account.
I've looked into laser liquid cooling and automotive liquid cooling for transmissions.
While both approaches
-are probably gross overkill as few processors produce anywhere NEAR the level of power to dissipate as autos or heavy duty lasers,
-will probably require some kind of external setup limiting it to desktop only,
you can be sure that the cooling system will keep on cranking out for whatever punishment you give it.
The laser coolers are much more expensive new and it's rare to find a good surplus deal let alone surplus at all. But with an array of peltier/thermoelectric coolers and sensors controlled with a dedicated microchip processor and/or program with your system, it certainly is possible to make a powerful sophisticated cooler out of a kludge.
Automotive transmission coolers acting as mini-radiators have also been used. Some second cousins of mine did this, actually. Worked quite well. I swear by it. Similarly works like those for computers but quite outperforms them. Reasonably priced too.