Well the main advantage of an SSD is the speed of it, in theory it should also be less likely to break as it has no moving parts but I think that there is a history of them breaking, I'm pretty sure they are a lot more reliable nowadays though. It is necessary to have a CPU cooler regardless of what you are doing however the CPU already comes with a cooler. Reaper specced the OEM version which doesn't include a cooler so it is a little cheaper and then he chose a cooler which would have a much better performance than the stock one which normally comes with the CPU.
From the way you have asked I think you are moving towards not overclocking your CPU. I think that once you have had the system for a bit and if you look into it and see how easy it is to overclock a 2500k, you may wish you had got the better cooler in order to clock the CPU a lot higher. If you definitely don't want to overclock then there is no point in getting the 2500k version, the 2400 is identical however is cheaper but doesn't allow overclocking.