I am studying the exact same thing for my own HAF 932 case.
The HAF 932 case is designed to push air in from front to back. Ideally your drives at the front of the case should be spaced to allow intake air to flow around and in between them.
Next you need to consider which way your PSU exhaust air is blowing. If you mounted yours on the bottom like mine, then it will most likely be exhausting its air out the back...not a bad idea as this keeps the heat out of the case. If you mount a fan in that optional fan spot on the bottom of the case then you will have the air from the front being directed upwards to the ram slots and the CPU heat-sink. Having the case panel side fan(s) will allow sufficient cold air to be blown towards and drawn in by the PSU, GPU and the heat-sink as well.
Now if you are interested in over-clocking your CPU then it is recommended to ditch the stock CPU cooler and buy a good after-market one. Seeing as most after-market coolers range around the same cost, I would recommend buying one of the best rated ones. A good site to help you choose is http://benchmarkreviews.com
I myself have an Intel i7 920 and therefore I purchased the Thor's Hammer heat-sink (rated 3rd) and bought some Enermax Magma fans to attach to it. Typically if you want better cooling on an after-market heat-sink you need to buy fans that push more air (CFM), but typically these are louder. I recommend fans like mine that have a good sound rating with low decibels, yet still maintain a good CFM or air push.
Now the question is which way to mount the heat-sink right? You have 2 options. Either you mount it from front to back or you mount it from bottom to top (this is in regards to the direction of the air flow as per the attached fans.) Oh yah...2 fans on a heat-sink should be set in a push-pull configuration, as head to head does not work that well, just like vehicle traffic ;)
The above question does not come in to play however if your heat-sink fan blows air directly onto your CPU, such as the stock LGA 1366 model like the one my CPU came with. If you plan on using a stock cooler like this then do not remove the fan as case airflow will not be hindered by it and without it your CPU may overheat and melt. Here are some videos demonstrating the importance of a CPU heat-sink:http://www.youtube.com/watch?v=Xf0VuRG7MN4
Case airflow may not be enough to cool the heat-sink alone and therefore I would not risk removing stock fans from either the CPU or GPU.
Now back to the top-bottom vs front-back question. Your best bet is to go with a front to back configuration. Why? because as your picture demonstrates, the HAF 932 is engineered to pull air in from the front and side and then exhaust it out the back and top of the case. Having the fans in this same configuration will allow the front fan to pull cold air into the heat-sink (air coming up from the optional bottom mounted fan, side and front fan(s)). As it passes through the heat-sink, this air current will then collect heat from the CPU and the rising heat, if any, from the PSU and then push this warmer air towards the rear exhaust fan of the case. Any heat that does not get caught in this current will eventually be sucked out of the case by the top 240mm fan.
So there yah go....simple answer = go with a front to back configuration for your CPU cooler and its fans...depending on how it is designed of course. If you need a picture of how my build will be set-up as a reference or example...just give a duck call :)