Tom’s Hardware has been doing a feature for the last week comparing the performance of six systems: budget (sub-$1000), mid-range (sub-$2000), and high-end (sub-$4000) PCs and then the same PCs overclocked as far as they’d go. The object was to find what offers the best value for the dollar. They ran about five billion tests, but I’ve got the Cliff’s Notes here. And the survey says:
The low end machine wins — sort of by default. Because most games were basically playable on <$1000 of hardware, that's what really matters and then what you start paying for is rapidly diminishing returns. In the end, they determined that to double the performance of the budget PC, you triple the price, or more. Fortunately, you're not bound by the rules of their experiment, and you can spend however much you want. I'd say the real winner is the mid-range overclock, since that’s what I’m running. You can still get a lot more performance and OC potential up to about $1500, I’m thinking, but after that you’re moving into the ridiculous zone.