I've got most of my parts for my first build, based on an i5 2500k processor and a Radeon 6870 GPU. My case is a midtower ATX. I'm not sure of the brand, but it looks like it has fair ventilation.
How many fans would be sufficient to keep the system relatively cool?
In addition to the heatsink, do I just need grease? What should I get that would work but be fairly cheap?
Is it pretty easy to swap heatsinks if I wanted to upgrade to something more significant in the future? I'm probably going to want to overclock at some point, but right now I just want a nice stable system, as it's my first build.