Before i say anything on this matter, bill please dont rip my throat out for my following suggestions..
Since getting exact numbers for rad testing that are generic and are useful and mathematicaly aplicaable to a wide variety of setups seems just about darn near impossible i thought of coming up with a stanardized test setup in which a number of rads could be tested on, and compared to eachother on this setup. the numbers would not be aplicable to other systems (obvously) but it would help to give us a judge of how a rad will perform compared to others in respect to pressure drop (no exact numbers on pressure drop, but relative restriction), heat disipation and various flow rates and heat disipation at various fan speeds and types.
The test setup would be a cpu block mounted on a cpu with the thermal diode mod or a die simulator, along with the block inlet temp. Flow meter, rad inlet temperature, rad outlet temperature, a powerful pump to test as a various flow rates, and the other odds and ends in a normal loop.
With this you could get the the affect of the rad on cpu temperatures, the amount of heat the rad is removing from the water at a given flow rate, and the flow rate. Obviously room temp would need to be kept constant for all of the tests, but with this data you could get usable performance numbers for rads.
So now that I have given my idea for rad testing, feel free to tell me im a moron and that this will not work. (bait)