yeah, Dell learned to put good PSU's in their systems a couple of years ago.....saved them no end of problems with returns when customers had extra things fitted from Dells online store (ie more memory, extra disc drive, upgraded graphics card etc)
Dell rate their power supply quite conservatively......my 8400 has a 350watt PSU, but happily runs my 6800GTO at Ultra specs (disregard my thingy below, im currently running it at 400 core and 1100 memory...lol....gets a little hot cuz it uses GT cooler, but i have an internal case fan blowing on it with a thermal exhaust fan in the PCI slot next to it...heh). Given the Ultra specifies a 400-450watt PSU to be on the safe side it means the Dell one must be more like a 450watt PSU if you compare it how they rate them on tech e-tailer sites....
to be honest i wouldnt be surprised if nVidia ignore the AGP market......some people might say that stupid, but to be honest, most people owning a system worth putting a card that powerful in have probably upgraded to PCI-E anyhow....they still have their 6xxx ranges to sell in AGP, they might even continue to manufacture those and rebadge them MX's.....(be amusing, knowing your slotting a 6800 Ultra in to your AGP mobo, yet it says 6800MX on the cooler....lol)