I'm considering buying a Dell XPS 7100 prebuilt system out of sheer convenience and price. The CPU/GPU combination I would get is the AMD 1075T / ATI 5870. The only thing that really concerns me about the computer is the scanty 460W PSU.
The review on the XPS 7100 from anandtech says that the computer is pretty efficient in power usage and the PSU will not likely pose a problem unless future upgrades are planned.
However, according to this calculator, with my setup, a 500W minimum PSU is recommended: http://support.asus.com/PowerSupplyCalculator/PSCalcula.... This makes sense, considering that the 5870 can reach ~350W under maximum load, and gives a usage higher than 460W when combined with the 125W CPU.
Does anyone have any insight into this issue? I do know that it is possible to replace the PSU in Dell's XPS 7100 without voiding the warranty, so some options I have are to just buy the computer and use it as is until a problem presents itself, OR to immediately upgrade the PSU to a ~600W one.
Lastly, how would I go about finding a compatible PSU? Would I have to open the case and note the physical space available in addition to the connectivity?