the sapphire 7870 come with 6 pin to molex adapters so you wont need to worrie about how many 6 pin connectors your psu has .
i personally will be running 2 of these already have 1 overclocked and get pretty decent numbers so far my best bench mark on 3d11 perfomance is 8450 i planning on a 13000 + score after the second card comes in .
the 1 7870 ghz oc edition that lets my play planetside 2 on max settings and still get fps between 55-160 fps with v-sync and smoothing off shadows low, everything else is on max settings. using an amd fx-8350 cpu
will i need a better power supply then this one to run crossfire 7870's ?http://www.newegg.com/Product/Product.aspx?Item=N82E16817182278
and if your absoultly sure it wont work, can some please provide a fair priced psu that will work.