The powermongers here don't want to hear this:
Dell PSU's are pretty powerful. If your system isn't heavily loaded (only 1 or 2 HD, very few USB devices hanging off it, etc.) then it may be adequate to power the card.
Why? Most PSUs are crap. They may say 350w but that rating is max power, and they can't keep up max power long before burning out. They can only produce 70-75% of the power rating continuously. Dell's PSUs are rated at continuous power. That means they can put out 250w continuously. That 350w that nVidia wants, after adjusting to continuous power levels (350 X 0.75), is 262.5w. Pretty darned close to what Dell has.
I would give your current PSU a shot. Load it up, give it the toughest game (not necessarily tough for you, but most graphics card work) you have, and have a test for a few hours. If it works, is stable, doesn't crash or give any warnings, etc., then you have enough power.
Mike.
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