Well, the 550w will be enough wattage to run that card, I was just wondering about the amperage that you have with that psu. Hopefully you'll be fine. When you get your card and install it, ensure that the power line to the card is clean, meaning that there is nothing
else plugged into it. If you get jumbled graphics, then you know that you'll need a new psu, one with 18 or 20 amps on the +12v line. A name brand one (probably exspensive) is the best way to go.
Also, with your ram, make sure that you get the same speed ram. Getting the same brand would also be a good idea, but not a requirement.
Hope this helps!
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