all high end cards are similar deals. Nvidia and ati both make good cards. Nvidia may run a bit hotter(which should eliminate the need of a frying pan ) and consume slightly more but have good sli scaling, amazing single monitor performance, CUDA, PhysX and 3D vision.
^^ lulz tru say.. the SLI scaling IS awesomeness! But dont forget ATi is also going with the 3D thang, + with eyefinity WOOOOOOOOOOOOP! Besides... How many games are worth buying just for the nvidia gpu? 1-2 at most. (Imo )
yeh agreed with the psu... the StealthXStream is just not efficient enough. (Specially if your going Nvidia)
Like Transmaniacon said the Modstream is far better. Just get something 80Plus certified, it's a must have.
Bottom line for the nvidia / ati thing, Go with whats within your budget (after you've chosen core-parts) if you can afford the Nvidia (480) then by all means GET IT.
Just keep in mind, the Ati IS cheaper, runs cooler and Less power-hungry at the cost of 5-10% performance - Bar the SLi scalling. Then saying that, it's nothing drivers wont eventually cure. For me it's a winner...
When, and if, you chuck another 5850/70 in there it will be more than ample at playing ANY game out there with full eye-candy! even metro2033! (youtube it!)
Yeah ATI is definately a viable solution but a simple downgrade to an i5 which still provides ample power(because only when the cpu works alone will you actually see a difference because all other components will bottleneck you're cpu) could bring you below your budget even with the 480 and a better HDD.
160GB is really too small for a HDD. For $54.99 you can get the Samsung f3 500GB. This an extra cost of $16 and it will give you much more space and even a small performance boost. I would keep the case, but get a better PSU (Corsair, Seasonic, etc.). These two things would add a bit of money, but be worth it.
To save, I would go with the Radeon 5870 instead. If you are going to be using the computer for gaming, movies, etc. just go with the i5 750 instead. You won't need that much CPU power.