Memory decision

[Mayboy]

Hiya guys, I currently have 2GB of 667Mhz DDR2 in my PC and was thinking of buying faster memory but would it make that much difference? I'm looking at either 2GB of 1066Mhz (considering the price of it) or going for 4GB DDR2 800Mhz, what choice out of those two would you recommend.

Thanks in advance.

 

[Twist86]

I can't tell a difference between my ram underclocked to 667mhz to my ram OC to 1066mhz. So I left it @ 800mhz.

Not to say there isn't one but I didn't notice any kind of difference.