<<< System Summary >>>
> Mainboard : Dell 0R849J
> Chipset : Intel X58
> Processor : Intel Core i7 920 @ 2666MHz
> Physical Memory : 8192MB
> Video Card : ATI Radeon HD 4800 Series
> Hard Disk : Western Digital WD6400AAKS-75A7B2 ATA Device (640GB)
> Hard Disk : WD 5000AAC External (500GB)
> DVD-Rom Drive : HL-DT-ST DVD+-RW GH30N
> Monitor Type : PL1900-BK - 19 inches
> Network Card : Intel 82567LF-2 Gigabit Network Connection
> Operating System : Windows (TM) Vista Home Premium Home Edition Media Center 6.00.6002 Service Pack 2 (64-bit)
> DirectX : Version 11.00
> Windows Performance Index : 5.9 on 5.9
It wil run with that psu, but a i7 920 is worth a better card than a 6770 imo. Depends on if you wanne game with it, if so i would buy a nice 500W psu from Antec, Corsair, XFX or Seasonic and put a HD6870, GTX560Ti or even a HD6950 in it. ( if your gonne upgrade in 1-2 years the 560Ti is the best choice i think.
I have about the same system as yours. Mine also has a cpu ventilator with a big round thing on it ( can't think of the English term ) going to the side of the case so it gets cold air from the outside. Also 1 fan blowing air out. I have a 560ti soc which get's pretty hot but without problems for other components. I checked the temps inside a couple of times and it was ok.
I believe I have some sort of fan sucking in from the front-side vent as well. I will have to double check it. If I do have that, I think i'll go with your suggestion of the 560ti. Thanks again for helping a newbie.