Depending on how old your psu is you might want to upgrade it before you drop in a pricey card like the 7870 in your rig.
If your psu fails it could take you new card with it.
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PhenomII 1100T// Asus Sabertooth R2.0 // 2X HD5850 CF //8Gb of 1866Mhz ram, H50 cooling, HX850W psu all stuffed into a NZXT Phantom case.
Was a member of AMD Processer forum since 2008. Last post count 1818.