I think the higher voltages mainly cause damage to the CPU, though I'm not terribly sure.  Raising the clock by itself shouldn't be too big an issue.  When you raise voltages, you also increase heat generated by the CPU, which is where the coolers come in.
For Intel chipsets (ie your X58) the RAM is typically linked to your CPU clock, so overclocking the CPU can overclock the RAM.  They changed the FSB thing with the i7 (called QPI or something like that) so I'm not sure how these things play out.

Also, don't leave your voltage at "Auto" if your mobo has the option - it gives far too much voltage.