Would running an air to water be enough?

I know its not the same but in the Subaru world I've always heard air to water is better. I always thought you ran it from a separate water source, not your engine coolant, and would have a cooler in front of the radiator. The heat transfer properties of water are better than air and can pull more heat from the intake. I know that heat soak becomes a problem over time and I could see how it would be a bigger issue with a diesel.
If I am totally off base feel free to inform me and by no means am I some ricer kid trying to show how big my balls are. I have a Subaru Legacy wagon. The most un-ricer turbo Subaru you can own.