dr_zukov,
i run a P4 2.53@2.9 and also cool my GPU as well with the same loop, both copper Danger den blocks.
I then run the tubing out of the rear of my case across the other side of my bedroom and on top of my wardrobe. The total loop is about 7 meters. I drive this with the tiny Eheim 1048 pump.
My rad is passive and aluminium and i have had no corrsion in the 3-4 months it has been running!! It is definetlay do-able. To prevent corrosion i have been using a car engine coolant(with anti corrosion inhibitors)/soft water mix.
Onto my rad, as im sure that's what you are interssted in, is from a Ford Fiesta and cost me £1 brand new on E-bay, im sure you will know that car being in Europe. Note it is the main radiator, and not a heater core!!
With the above mentioned system, the max CPU temp i have had is 50 degrees C with an ambient of around 36 degrees C under full load, it only drops to about 40 degrees idle thought. Certainly OK for the complete silence!!!
Here are two Links, the first is a post on my "local forum when i first set it up (a lot has changed since then).
The second are some pics of my initila setup. (again, it is now very different)
http://www.pclincs.co.uk/Forums/show...&threadid=2340
http://uk.msnusers.com/WaterCoolingRelatedStuff/
Hope i have been of some help,
Kristian