1.8 is very high for a x58 board. Remember that the VTT has to stay within .5 of the Dimm voltage. I'm not comfortable with it being that high and intel specs are 1.65v for the RAM I believe. Mem controller on 920 may not be strong enough for 1.8v either.
Yup as long as you keep it within .5 VTT you are fine.
Intel specs are for 1.35 or 1.38 max VTT IIRC.
So to me that was a starting point And as long as everything is balanced and you keep stuff cool you will be okay.
As far as ram goes... that kinda high voltage for DDR3 is not common.. must be some especially bad ICs.. dont know of the top of my head. Rip off the heatspreader if you cant google the info and find out what ICs are on there.
If still not good. (OCZ rebranded) OC them see what needs what and google some more,... figure out what ICs they are based on performance clocks at volts... and get a good idea of what they CAN do.
I pushed my cheap *** sticks above 2.1 Gigs at 1.9 volts. 9-9-9 2Gig at 1.875 8-8-8 and ran them routinely at 1.8-1.85 7-7-7 from 1700 -1800