I plan to over clock a E8400 on a X48 board...and I am trying to see which of these will be best?  I heard 1066 is a buffered 800 for DDR2...is there any benefit to buying 1066 over 800 at this point?  The price difference between them isn't an issue for me.  The motherboard is LANPARTY DK X48-T2RS http://www.newegg.com/product/prod [...] 6813136047
 
Here are my choices for memory, voltages seem to vary.  
 
OCZ Reaper HPC 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) OCZ2RPR10664GK
Timing 5, 5-5-5-18, Voltage 2.1V
http://www.newegg.com/Product/Prod [...] 6820227289
 
(2) OCZ Reaper HPC 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) OCZ2RPR1066A2GK Crossfire Certified
Timing 5-5-5-15, Voltage 2.3V
http://www.newegg.com/Product/Prod [...] 6820227239
 
OCZ Reaper HPC Edition 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) OCZ2RPR800C44GK
Timing 4-4-4-15, Voltage 2.1V
http://www.newegg.com/Product/Prod [...] 6820227267
 
(2) OCZ ATI CrossFire 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) OCZ2A8002GK
Timing 4-4-4-15, Voltage 1.9V - 2.1V
http://www.newegg.com/Product/Prod [...] 6820227169

OCZ Reaper HPC Edition 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) OCZ2RPR800C44GK  
 
would be my choice of those... as its the lower timings with the most quantity

^Agreed.  
 
@OP:  
If you are planing on getting RAM natively higher than DDR2 800 be aware that there will be compatibility issues. Many users reports and my personal testing has shown that there is a very good chance you will run in to issues with RAM higher than DDR2 800, such as DDR2 1066. I recommend you get quality DDR2 800 RAM and run them at 1:1 ratio or overclock the RAM. This issue dose not apply to DDr2 800 RAM that has been overclocked.

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E2180 @3.2Ghz + P35DS3L +8400GS (700/475 OC)