Crucial vs Crucial and a few other questions

I'm looking to build a new system and wanted to know which would be better for overclocking

Crucial Ballistix PC2-8500 DDR2 2GB 2X1GB DDR2-1066 CL5-5-5-15 240PIN DIMM Dual Channel Memory Kit
or
Crucial Ballistix PC2-6400 2GB 2X1GB DDR2-800 CL4-4-4-12 240PIN Dual Channel Memory Kit

I was going to buy the Corsair Dominator 8500 but its a lot more expensive than these Crucial sticks. Here is what my system will look like:

EVGA 780i SLI
Intel Q6600
EVGA 8800 GTS 512 crysis edition x2 SLI
OCZ GamerXtreme 700W
4 hard drives
Thermalright ULTRA-120 Extreme 6 Heatpipe Cooler LGA775 Heatsink
Scythe S-Flex 120mm fan for CPU and 4 other case fans
DVD Writer

So I have 3 questions
1. What RAM will work better for OCing?
2. Does the 8500 RAM work better then the 6400RAM or do the timings mean more c4 to c5?
3. if I get any of these can I get 2x2GB for 4GB or should I only get 2x1GB so less stress on the memory controler?

On a side note I came across this http://www.evga.com/support/mbmem/ and don't see the Crucial Ballistix PC2-8500 DDR2 2GB 2X1GB DDR2-1066 CL5-5-5-15 240PIN DIMM Dual Channel Memory Kit listed, anyone else have a 780i board and use these?

Thanks!

Either will work equally well.
No need to spend anything special on your DDR2-800 since straight DDR2-800 will take the Q6600 to 3.6Ghz which is about it's max.