You can use the same type of RAM I originally recommended to you. You can always upgrade your memory to 4 gigabytes of PC2 8500 later. 4 gigabytes of PC2 8500 is going to run you about double of what you would pay for 2 gigabytes of PC2 6400 memory. (I personally prefer Patriot RAM as their products are made in the U.S.A.) 2 gigabytes of memory should be enough.
Patriot Extreme Performance 2 gigabytes (2 x 2GB) 240-Pin DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory - $27
http://www.newegg.com/Product/Produc...82E16820220174
Also, don't forget the other components in the list that I originally recommended to you that aren't in your present list.
Edit: Here is a fixed link:
Patriot Extreme Performance 2 gigabytes 240-Pin DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory - $27
http://www.newegg.com/Product/Product.aspx?Item=N82E16820220174
If you want to buy 4 gigabytes (4096 megabytes) of PC2 6400 RAM it will cost you $23 more.