Based on an earlier case migration I did for my Dell, somebody asked me a question about changing the power supply.

Is the dell dimension 8300 utilizing a standard ATX pinout or is it Dell's custom wiring schemes, and if it is dell's custom wiring do you know of any adapters? and if it is standard atx should I use a standard 24pin to 20pin ATX adapter to allow the Ultra X3 power supply to work.

So the short answer is that any power supply should work just fine, in fact I'm using an Antec Phantom 500 myself with no issues. Usually you can even break off the extra 4 pins to magically make it a 20 pin one without using an adapter.