power connector for 4th HDD in T3600?

My T3600 has 3 power connectors for HDD's and 1 for the ODD but it is a different style plug (it branches off of another, regular HDD power plug in the ODD bay).  How can I get power to a 4th HDD?  Is there a way to run a splitter cable from an existing end or will this be to much of a drain on it?  Any way to convert or step down the unused 6-pin video card cables?

BTW, one of the 4 drives is a SSD and I have the 635W P/S.