I have a Dell XPS 8500 that I bought last winter and I am looking at upgrading the GPU on it(it came with a 6770) for playing more intense games, such as crysis 3 when it comes out. I want to know if the 460W PSU it came with will be enough for changing the GPU to a 7850 or 7870. I have used a PSU calculator and it looks as if it's only using 320W maximum with its current setup.
The 7870 144W at maximum load compared to the 7770 which only uses 83 according to techpowerup.
I have heard that Nvidia uses less power than AMD cards, so is there a Nvidia card similar to the 7850 or 7870?
Thanks, I can provide extra info if you need to know anything else.