I've done some research about some PSUs and the mentioned cards... and found out 550watt power is more than enough for me. Then I just removed my last question about PSUs.
But I'm not sure about Graphic Cards yet.
That "SAPPHIRE DUAL-X R7 265" has 256bit bandwidth GDDR5, and I thought the solution is to choose this one...
And another strange thing is that 256bit GDDR5 Memory on "R7 265" is just 200MHz faster than the "750 Ti 128bit".
(MSI N750Ti TWIN FROZR IV 128bit 2GD5/OC) with 5400Mhz
(SAPPHIRE DUAL-X R7 265 2GB 256bit GDDR5) with 5600MHz
How about that?