So I have a couple of questions about DDR2 RAM.

1. Can you see much of a DIFFERENCE in performance between DDR2 800 (PC2 6400) and DDR2 1066 (PC2 8500)?

2. Which is better to have, more of DDR2 800 RAM or less of DDR2 1066 RAM? Which will show greater performance: 8GB of DDR2 800 or 4GB of DDR2 1066?

By the way, either choice would be PAIRED with an AMD 9950 Quad Core.Depends greatly on the MBoard...i have had both in my new BUILD...
Equal amounts/Faster speed = no noticeable difference
More RAM/same speed = noticeable difference.

The same holds true with the new DDR3 RAM as well.

Summary: More = Better.Adding to the excellent post above:
I doubt you'd see the performance difference between 800MHz and 1066MHz, except in benchmarks.
More RAM at a slower speed will almost ALWAYS be better than less RAM at a slightly faster speed - DDR2-1066 tends to come at a premium price too.
If you're after 8GB of RAM you'll need a 64 bit OS to benefit from it too.
Hope this helps.BTW i have 2G of OCZ 800 with cooler fins available SINCE i just got 4G of 1066 at a closeout price....
If anyone's interested.