If you look at the bottom 3.5" bay my harddrive is right there.
As far as my system temps, I didn't notice any diffrence what so ever... Actually they went down some. The water isn't hot like in a car.
The heat coming off your radiator isn't half as warm as the heat coming off of a heatsink... When I went water cooling, my system temps cooled, my vid card temp dropped a little, and the air coming out of my PSU is much much much cooler.
Hope that helps. I think the main reason I seen drops was that 120mm fan really moves air around in the case. With all my fans turned off in my system, my case temps rise to about 32C and my CPU idle temps are around 27C (halt command)
I love the halt command with my new 8k3a+ my CPU idle temp is the same as my water temp going into my water block.
And with that, when I don't have a load on my computer. I can practically turn off all fans in my system.