Do NOT get any RAM that runs higher than 1.65V. Intel rates that as the absolute maximum spec for running RAM without damaging your CPU or motherboard.
You may want to base the frequency of RAM (e.g. 1333 MHz) you select on your CPU. If you get an i7 860 or i7 870, you can run RAM up to 1600 MHz at stock settings. With an i5 750 or a Clarkdale CPU you can run RAM up to 1333 MHz, any faster requires OCing your CPU.
If you don't plan on OCing, you may still find 1600 MHz worth purchasing - for example, sometimes it is cheaper than similarly spec'ed 1333 MHz RAM.
In general, look for lower voltage RAM with the tightest timings (e.g. CL7) at your price range. The basic recommendation from the first article I linked to is "Make sure you pick a branded product of at least DDR3-1333 speed and timings of CL8 or faster". Give it a read and you'll understand why.
The 1.5v is the "auto" setting for that motherboard. After you install your RAM, and before you go on to install your OS, get into the BIOS and change the voltage to the specs of the RAM.
Regarding changing the setting for memory, what if the motherboard doesn't allow you to adjust down. I am using the Gigabyte 790X
t-UD4P motherboard it has set my voltage to 1.65 and looks like I can only adjust upwards.
The RAM V warnings for not going higher than 1.65V apply to Intel 1366 and 1156 socket motherboards. I don't know as much about the working of the AMD boards so I'll let someone else answer. But it might be helpful to know, what RAM do you have? Please provide the complete model number and a link would be helpful, too.