Both R9 270 and R9 270X , should work on the PSU . it has 2x 6+2 pin power connectors and 37A on +12 V rail or 444W .
GTX 960 - 120W
A10 6800W - 100W
other 100W
------------
320W , it s the best option
R9 270 has TDP 150W , or system power draw = 350W
R9 270X has TDP 180W , or system power draw=380W
So , all three cards should run on the PSU .
R9 270X is up to 10% faster than R9 270 .
But GTX 960 is on par with R9 280 !
http://de.pcpartpicker.com/part/gigabyte-video-card-gvn960ixoc2gd
http://www.super-flower.com.tw/products_detail.php?class=2&sn=18&ID=106&lang=