More, dare I say it, bang for your buck.
If you can spend $20 on better cooling for your CPU and overclock by a couple of hundred megahertz then you will get more performance/throughput than without. For instance one of the most popular overclockable processors in recent memory is the Intel P4 1.6A (A = Northwood core). With the default Intel Heatsink and Fan some of these overclocked to over 2.2Ghz (thats an amazing increase 600Mhz or more. So its like getting a 2.2Ghz P4 for the price of a 1.6Ghz (which at the time was quite a bit less expensive than a 2.2Ghz P4.