400w PSU for 4890?

Just got a new GPU and wanted to know what you guys think, if its safe.

I'm running:

e6750 @ 2.66GHz (lowered from 3.0GHz in case not enough power)
4x1GB DDR2-1066
ATI 4890 1GB DDR5
2x500GB HD
6-7 USB devices

I calculated this on the PSU site and came up to about 350 but when I go to the gigabyte site, it says 550w. my system is currently running pretty smooth. However, I upgraded from a 9600GT, windows rating was 6.9 for the 9600GT and 6.0 for the 4890... but I see the difference in gaming, anyone know whats up with that? Thanks guys.
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More about 400w 4890
  1. We need efficiency rating on the PSU, amps on 12v rails. A model number on the psu will do fine most of the times.

    Windows rating should be ignored point blank. The Hd 4890 is superior to the 9600 gt, however your psu could be limiting the GPU post more information please on the PSU.
  2. Best answer
    If it is a high quality PSU with about 30amps on the +12 volt rail, like this one you are fine.
  3. oh sorry guys, forgot to post that. I'm running the exact one posted above.

    So could I clock my CPU back to 3.0GHz?
  4. Give it a try, all you get if you reach the limit of that psu is random reboots.
  5. I'll give it a wurl in a bit, anyone know if 3dmark06 is reliable? I got a SM2.0 score of 4388 and on the charts its showing the HD 4890 should be about 7300s. Is this a problem?
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