if you can afford it get pc 3200(400mhz) Corsair is at the moment the best on the market but also a little pricey. I would suggest mushkin to be your second choice if you have to save a little money..... Corsair: 256: Cheapest from Pricewatch.com 512 : Cheapest from Pricewatch Mushkin: 256: Meduim Performance 512: Meduim Performance of course if you want higher performance, like the best available there different cas settings that your motherboard will take, but again the best thing for you to do is to set a price you want to spend on RAM and then go for there. I paid a little over $210 for my stick from corsair. Of course that is the fastest out there.