This PSU will work perfectly fine with the GFX card, theres no need to worry too much about amps/voltages, The card requires a 550watt or higher PSU, 675 is easily enough.
The PSU has modules for 6 and 8 pin connectors, the GFX card requires 1 6 pin and 1 8 pin.
However the following 2 have a higher reliability rating (80+ silver 88%)
there a little more expensive but have a much higher ammount of modules and the 750 watt version will allow you to upgrade even further (2nd graphics etc) if you need.
I wouldn't worry about Bronze versus Silver; there is no issue with the TP XT being a Bronze rated PSU. If you already have the XT 675W, then don't worry about replacing it - it is sufficient to power the 6970.
Thermaltake isn't one of the more highly recommended brands because of some reliability issues. People tend to recommend Antec, Corsair, or Seasonic for excellent reliability/performance. Proximon has a recommended PSU thread for some more detailed info if you want to do some more reading. Again...there is no need to replace your PSU - it has sufficient power for your intended GPU.