The sidesaddle bays in my Rosewill R5604 allowed my HDDS to be kept cool enough. As far as the fan helping cool the rest of the system, there is where there won't be a lot of help. Just make sure that there is enough extra venting near the front so the exhaust fan can draw sufficient air to do the job. Check the rpm of your rear fan with the side panel off, then put the side panel back on and check the rpm again after a while. If there is a significant drop, then you need to free up some venting.
.bh.