Ehh, the OP asked for a GPU that's recommended for this exact CPU, the Intel Core 2 Quad Q8300 and not criticizing him using "ancient" systems and such.
My vote goes to the R7 265, it isn't that much expensive over the GTX 750Ti, it's a bit more powerful with the con that it may use more power but that 550 watt PSU should handle it without much of hiccups.
If power consumption and money is the factor then consider the GTX 750Ti. It's cheaper, efficient and powerful (for it's category).