I am thinking to upgrade my Vcard to either a MSI 7970 or a Saphire 7970 but not sure if my Phenom II 965 BE OC@ 4GHz can handle them without bottlenecking or I have to upgrade to 4300 or 6300 vishera.
Please do not sugest intel as i am not planning to upgrade my motherboard by now.
It will bottleneck it although you should still be able to play games at 60+ fps in most games. In my opinion the difference between a 965 and a FX 6300 does not warrant an upgrade. I advise you to wait for the AMD steamroller CPU's (should be out by the end of they year) because the indications are that the chip will have even better multitasking performance and single threaded performance will also improve dramatically to the point where it will compete with Intel Haswell.
It depends on your resolution if its under 1920 x 1080 then the CPU will be a large bottleneck @ 2560 x 1440 then not much at all. It will also depend on the game, like Metro will nearly always be limited by the GPU.