Memory rec. for Gigabyte 970A-D3 mb

[phix95]

My info:
MB: Gigabyte AMD 970A-D3
RAM: Kingston DDR3 SDRAM
Video: ATI Radeon HD 4800 Series
CPU: AMD Phenom II X4 955
Win Vista 64bit

My current memory is 4 gb, in 2 gb modules. Brand is Kingston DDR3 SDRAM. According to Speccy, the speed, well max bandwidth, is 667 mhz. But above that, it has the DRAM Frequency as about 2600 mhz. I'm not a newbie but no expert. So that's a bit confusing. Seeing some benchmarks on the mem I have, appears like it's not so good.

My pc is too slow so looking to add maybe an 8 gb stick. So just looking for some rec's.
My pc (a custom build from Cyberpower) is from 2009. Over the years, I believe I've replaced the MB, the heatsink, the vid card and power supply. I just lost my job so price is an issue. I'm a designer and a gamer so looking for a good compromise of price vs speed. Prices seem to really vary depending where you go.

Thanks

 

[popatim]

get two 4gb's instead and be sure to install them in the correct slots so that dual channel ram is/remains enabled.

 

[phix95]

get two 4gb's instead and be sure to install them in the correct slots so that dual channel ram is/remains enabled.

Why do you suggest 2 over 1?

 

[popatim]

one would turn off dual channel and cost you up to about 10% performance. And you already said your pc is too slow...