I just ran across this thread while searching for something else, and since it's not too old I will put in my two cents.
I bought one of the aluminum radiators off ebay, and it works fine and fits just like factory one. It is a whole lot lighter than the original radiator.
One thing that hasn't been brought up is the coolant. If you are using the low silicate green coolant with the DCA's, you should not run a aluminum radiator or if you do decide to run a aluminum radiator or heater core, you should change your coolant to something different. The regular green anti-freeze has silicates to protect the aluminum parts in the cooling system, but of course we can't run the high silicate coolant with the DCA's because they cause sludge to build up.
I did some research before buying my aluminum radiator, and decided to start running Zerex G05 coolant. It's a hybrid that has aluminum protection in it as well as anti-cavitation properties. It's what Mercedes and some of the other manufacturers recommend for their engines. Zerex also makes a red coolant for fleet use that is even better than the G05, but it was a little too expensive for me. The G05 was around $9 a gallon from Napa, and the red fleet stuff was around $16 a gallon.