The danger with a cheap psu is that it might fail under load.
Worse, a cheap psu will not have the protective circuitry to keep from destroying anything it is connected to if it fails.
If your psu does not have the requisite 6 pin connector, it likely does not have sufficient +12v amps to support such a connector.
I might plan on replacing the psu regardless.
Or... why not use a GTX750ti(non overclocked) which is a equivalent performer and will run on pcie slot power alone?
It will be a nice jump in graphics capability over your departed 7730.