ASUS P5K or GigaByte GA-P35-DS3L
I Cant decide that even, any recommendations?
In either case you should check the QVL compatible memory on the manufacturers website and try to get RAM that is on the list. Understand that the 2G packs have additional numbers and letters on the model number. Here is the Gigabyte list motherboard_memory_ga-p31-ds3l_1.0.pdf. I'm using Crucial Ballistix 2GB DDR2 800 on a P35-DQ6 and it works flawlessly.
Well, Kingmax is 1066 on default, with 1.8V (I believe) - that looks promising. Others could probaly be OC-ed to that speed, but would need more voltage.
But in the end, I don't think it makes much difference.