[Q] Ati Radeon 7770 or Msi 6850 PE/OC

This has been quite a conundrum for me. Both are similarly priced about 8.5 k.
The 6850 beats the 7770 in almost all the tests. However the 7770 is a Directx 11.1 card and the 6850 is a DX11 card.My pc build will stay the same for about 3-4 without any major upgrade, so choosing a card has been quite a task. Help me out here guys. Also, please suggest a PSU which can handle it.

Final PC:
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Processor
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Intel i5 2400
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Motherboard
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Intel DH67CL B3
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RAM
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Corsair Vengeance DDR3 4GB(1x4)
-cmv4gx3m1a1333c9 1333MHz
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Hard Disk
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WDC Blue 500GB WD5000AAKX
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PC Case
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Coolermaster Elite 310
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Speakers
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Logitech z103
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Keyboard Mouse Combo
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Logitech MK200
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Monitor
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Benq G2222HDL
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UPS
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Intex 1KVA