I'm planning to build a new mid/high-end rig based on the G6600 G0 and an X38-based board (I'm thinking Gigabyte DQ6 -- thoughts here would be welcome too). I want to OC the processor to around 3.4/3.6 and run with 4GB DDR2 (yes, I'll be running a 64-bit OS). I'm looking at 4x1GB, 2x2GB, and two pairs of 2x1GB PC2-8500 memory kits. Which of these would provide the best performance/timings/OCing for my planned rig?
Gigabyte doesn't list G.Skill as a compatible memory, but G.Skill has stated that their memory is compatible with Gigabyte mobos. I can attest to this as I've used 2 different G.Skill kits in my mobo w/out issue.
Now everyone here is just giving an answer without explaining why it would OC better. Let me start by saying this, what FSB are you going to use to OC your CPU to 3.6 Ghz? You can use a 400 Mhz FSB with a 9x multipleir to get 3.6Ghz. PC6400 or DDR2-800 memory runs at 400 Mhz (DDR2-800 runs at 400Mhz x2, this equals 800 hence the name). This would say that you can run DDR2-800 memory without OCing it at all and still OC your CPU to 3.6 Ghz. The DDR2-1066 memory will run at 533 Mhz, you're going going to get a nice even multiplier at that speed and will likely underclock your more expensive memory. Also this more expensive memory will not have the nice tight 4-4-4-12 timings you can get with DDR2-800 memory. This will mean your more expensive memory may not perform as well as DDR2-800.
That being said, if you want a FSB higher than 400Mhz, still buy DDR2-800 memory and just OC it. This is what you think you need to do to the DDR2-1066 memory. But I would suggest keeping it simple and save yourself money and just use a FSB of 400 and get DDR2-800 memory.
Now what DDR2-800 memory? 4x1 or 2x2? 4x1 is cheaper. 2x2 is MUCH easier to OC with. Your motherboard only has to worry about 2 sticks instead of 4 and this takes the strain off your motherboard that is being pushed a little harder due to the OC. I would not OC memory, if you still are going to, with 4x1. I would only OC 2x2. It will save plenty of potential headaches.
The memory kit I'm using now is great, and it cost $160 shipped at Newegg. Its DDR2-800 and has 4-4-4-12 timings. It is the cheapest 2x2 kit with 4-4-4-12 timings I could find and is an excellent performer. It OC'd my Q6600 easily to 3.2Ghz, 400Mhz FSB x8 Multiplier. I just don't feel like going to 3.6Ghz, no reason to yet. G.Skill memory is also earning a good name for OCable memory as of late. This would be my memory recommendation.
One last thing with memory, DDR2-800 @ 4-4-4-12 will usually outperform DDR2-1066 @ 5-5-5-15. Tom's even did an article about this a few weeks ago, tighter timings are usually more important that higher speeds, especially since hardly anyone runs their CPU at a 533 mhz FSB.