Would like some opinions on what to do, currently I have some Kingston DDR2 8500 2X1GB kit, it works just fine but I have an opportunity to sell it and buy some different ram, my options are 2X2GB 6400 ram;

OCZ 4GB (2 x 2GB) PC2-6400C4 800MHz Reaper
OCZ 4GB (2 x 2GB) PC2-6400C5
OCZ 4GB (2 x 2GB) PC2-6400C5 Dual Channel Vista Gold Series

Or these;

Corsair 2GB DDR2 XMS2 Dominator PC2-8500C5 TwinX (2x1GB)
Crucial Ballistix 2GB (2x1GB) DDR2 PC2-8500C5 1066MHz Dual Channel Kit
OCZ 2GB (2 x 1GB) PC2-8500 1066MHz SLI-Ready Edition Dual Channel DDR2
OCZ 2GB (2 x 1GB) PC2-9200 1150MHz Reaper HPC Edition Dual Channel DDR2

The price difference between them all is small enough that it doesn't matter, my thoughts are what would be the plus and negative points of 2Gb or 4GB there is the difference of 6400 to 9200 DDR2 specs but would Vista 32 be better with 4GB or would Vista 64 be MUCH better with 4GB?

The reason I'm asking here is because I have this motherboard and really need to know how the different RAM is likely to run, I have read the whole thread and know the G Skill is very good but it's not an option as only the ram I have listed can I get at a good price.

Thanks for every ones input on the whole thread it's been a good read.