[airspirit]

The 512MB sticks will not clock as well. Ben is right. Consider this:

Use PC3500 memory in two 512MB sticks. I would recommend Corsair XMS, and get the stuff rated at the lowest timing rating you can find (low latency). When you pick up the fastest stuff available, it will probably clock as well as 256MB sticks of lower rated memory, and the NForce2 boards when run in DualDDR mode will give you another overclocking hit. Two sticks of low latency PC3500 will probably allow you to use decent timings when run at 200FSB or lower. Since you have diminishing returns over 200FSB (from benchmarks and other testing), I wouldn't recommend running it higher than that anyway.

2x512MB sticks will do you better than 2x256MB and 1x512MB anyday, though, when you consider the chipset you're using. This isn't really something that is debatable ... it is just the way it is.