thermaltake products in water cooling sucks....really. I have installed 10-12 of them, and all performed poor. I think its due to a crappy water block and/or an inefficient radiator. The cooper in the radiator comes pre-corroded...SWEET!
But the major factor with any cooling is ambient temperatures. Your fan, your radiator, you whatever needs cool air to cool down. The cooler the better. So if you are do H2O, make sure you have the coolest air blowing in to it. That is how achieve you gonna achieve maximum performance, because higher concentration of cold air = higher transfer of heat...