i think that is an overkill nowadays, same as RAM watercooling, unless you're overclocker that is only interested in overclocking over anything else.
i would suggest to do your own research on pumps, cpu waterblocks and radiators, can't fully trust sellers on that matter, they've got their own interest in the game.
that poseidon thing, can the fans be turned off if using water? or will they be another source of noise?