i got 1 gb of ram a 2800 overclocked to 2.37, 2 hard drives, and a dvd burner + a 5700. My 450 watt peice of shit sometimes shuts off my comp when it gets hot.
Get the thermaltake armor. http://www.newegg.com/Product/Product.asp?Item=N82E16811133154
or kandalf
http://www.newegg.com/Product/Product.asp?Item=N82E16811133152
both have room for a crazy amount of fans, and support a btx conversion kit.
It should probably be better, since it doesn't have the limitations that dell puts on their motherboards.
Since you can't increase the voltage, just decrease your speed.