SBMfromLA :
Suztera :
SBMfromLA :
What you should always do is go to the manufacturer's website and look up the specifications and requirements they have listed for accurate information.
I just looked up your card:
The XFX Double D R9 280 GPU
Requirements
External Power - 6-pins : 1
External Power - 8-pins : 1
Minimum Power Supply Requirement : 750 watt
XFX Recommended Power Supply : XFX 850W PSU
Source: http://xfxforce.com/en-us/products/amd-radeon-r9-200-series/amd-radeon-r9-280-double-dissipation-edition-r9-280a-tdfd
Manufacturer's will
recommend a higher wattage because there are low quality psu that are in the market.
A decent quality 550W will power almost any single graphic card. An exception would be AMD R9 390X and AMD Fury X where a decent 650W is preferred.
But what you failed to mention is.. if you ever have a problem and need to write a support ticket for a GPU.. the FIRST thing they will ask or check is whether you are using THEIR RECOMMENDED PSU... and if you aren't.. they will tell you to first upgrade to their minimum wattage before they would be willing to help you.
That would be the rep just reading from the script. There are plenty of prebuilt pc that will also use 550W-650W in a R9 280/R9 280X and they will still work. If you stated that you confirmed the gpu is at fault, they should not ask you about the psu, not that it matters if you have a decent one.
A decent 550W will power a R9 280 build quite easily.