Don't skimp on power supply, ever. A quality bronze rated or better with sufficient wattage for your build and possible upgrades as well. I bought the first TX750 corsair power supply for the upgrade reason. I have had it 5yrs and has done me well. Ran 2x HD 5850's prior to my HD 7970 I have now. You can cut corners a bit here and there on other stuff to a degree. Cases are a good investment but there is no need to go astronomical on the price for one either. You can get quality budget units that are sufficient for most people. Depends on your wants and needs. Monitors tend to outlast other components by a good deal, but you don't have to go crazy there either. What is your budget?