As far as the top part goes, you probably dont want the hot air from the radiator being blown into the case, even with exhaust. I'm trying a setup with the radiator in the back over the PSU and its fan outside the case, drawing air through. I also have a pair of 80mm fans (which fit nicely side by side in two 5" bays with a little plastic work) blowing in across two hard drives. It should be a good balance, the 120mm (Panaflo) pulls 69 cfm and the two 80mm's blow 35cfm each. I may even do a little ducting to make sure the air goes through the way I want. I'll post a modification of your pic in a few min.
As for the bottom part... I'm not sure, but you might want the 'in' fans positioned so they blow on your video card, if you do video overclocking too.
Hard drives usually dont get very hot if you keep some air going across them, I doubt they add enough heat to affect a radiator. Before I cooled my HDDs I had one get way too hot and stop working... luckily it was ok after it cooled awhile, but I'm not taking chances.