Hmm, I think the reasoning behind the setup I explained was that it is assumed the temp of the water right after coming out of the rad is cooler than the air temp inside the case. If that's true then if you have it go from rad to res before going to cpu, theoretically the water temp will increase. By how much I don't know.
Akira, are you doing a custom res? If so may I ask what the materials/design is going to be? If not, can you show me which one you would buy? Btw, I am inspired by your setup and now I really want to mount the res outside for many good reasons.