Machine rounded IDE cables greatly increase airflow and cool your case quite a bit. Basically by making this investment you're allowing everything else to work at capacity. Available in several colors so take your pick. Copper shims, fan, fan grills, thermal paste, etc. First up we have the copper shim.
Thermal paste is another issue.
Fan grills are also a necessity and sometimes a must. While not really needed inside your case, they work well to prevent your wires from being chopped up. And if you have a 7000rpm Delta fan make sure you get one else you'll regret it once you stick your finger in there for whatever reason. On the outside fan grills just look cool along with ensuring that things like pets don't get chopped up by that 120mm mofo. This is where most of your actual cooling comes from.