Hi there. I need help deciding the amount of memory for my PC.

My processor is the AMD Phenom x4 9950 Black Edition. Currently I have 2 sticks of 2gb DDR2-800 (making 4gb dual channel DDR2-800) RAM.

I am thinking of upgrading to Windows 7 x64, and I'm considering adding 2 more sticks, making a total of 4x2gb = 8gb in four slots. Problem is, adding in more RAM will reduce the RAM speed to 667mhz (also disable dual channel mode).

I understand I need to take the processor / FSB numbers to determine the optimum speed of RAM to use, but I don't fully understand how to calculate it, or if it even matters outside of benchmarking.

So can someone with this knowledge tell me, with my current processor (I mostly use it for gaming), will adding in another 4gb be worth the reduction in memory speed? Or should I stick with the 4gb to take advantage of the full 800hmz + dual channel?

Thanks in advance.