I've been using Gskill Ripjaw F3-10666CL9D-8GBXL (2x4) since I built my computer a few weeks ago. Unfortunately one of my sticks went bad (tested multiple times with Prime95 and computer would Bluescreen immediately or shortly after when using this stick alone) and I'm thinking of ordering another 8 gigs in (2x4) configuration. I'm just wondering if (1333) (10666) is the best way to go on an ASUS P8P67 motherboard.
Sandy Bridge does not demand only 1.5v modules, it will be perfectly happy with 1.65v modules too. If someone tries to tell you that you must have 1.5v modules, then they are either trying to sell them to you, or they have been reading misinformation, or both! Another point to consider here, is that in your BIOS, if you head to the memory voltage setting, and enter 1.5v, the text will remain white/grey, if you enter 1.65v, it will turn yellow, and it isn't until 1.73v that it turns red, so at the moment, I'd rest assured that 1.65v modules are OK to use, and I have had this confirmed by Asus, Gigabyte and Corsair so far, as soon as I hear from anyone else, I will update this again