Memory Upgrade

I am looking to upgrade the memory in one of my computers, Asus P5K-Deluxe MB with 2GB DDR2-667. The way I have been upgrading is to upgrade my main computer and pass the part I replaced to the other computers, sort of like hand-me-downs. My main computer has an Asus Rampage Formula X48 MB with 4x1GB DDR2-1066 Crucial Ballistix Tracers 5.5.5.15@ 2.2v. I would like to upgrade by replacing 2 sticks of DDR2-1066 with 2x2GB of DDR2-1066 giving this comp a total of 6GB with a future upgrade to 8GB or 4x2GB. I would then pass the 2 sticks of DDR2-1066 to the Asus P5K replacing the DDR2-667, which will also go to another computer. I have been checking the spec's on some memory trying to stay with the same timings and voltage. (see links below) The Corsair and ADATA have the timings of 5.5.5.15 but the Corsair's voltage is 2.1v and the Crucial is 2.2v Will the Corsair run at 2.2v with no problems or should I go with the ADATA which has a voltage spread of 2.2 - 2.3 volts.

Corsair
http://www.newegg.com/Product/Prod [...] 6820145214

ADATA
http://www.newegg.com/Product/Prod [...] 6820211291

Any advice, or recommendations, would be deeply appreciated.

MB: ASUS Rampage Formula X48
CPU: QX6850 3.0Ghz
HSF: Zalman 9700 LED
RAM: 4Gb BallasticTracer PC2-8500
GPU: VisionTek HD3870 512MB OC Edition
HDD: 1 x WD RaptorX 150GB / 1x300GB & 1x500GB Seagate SATA2
ODD: 2xPlextor 810SA DVD/RW
PSU: Thermaltake Toughpower 750W-PSU
Case: Antec 900
OS: Vista Ultimate64bit SP1

Shall i say none of those ?
I say go for a DDR2 800 RAM with 4-4-4-x or lower timings because the difference between DDR2 800 and 1066 isn't much and DDR2 800 OCs very good too.