Yeh Teleri,
The conclusions I came to before i bought my memory were
1 1.5v ddr3 gives you good compatability with the other p67 voltages tho there is eco ram at 1.35v
2 1800 mhz memory isnt rated that highly,has to be either over or underclocked for p67.
3 1600 mhz memory is the sweet spot in terms of price for some but there isnt much difference in going for 1333mhz
4 Unless your some kind of multi threading video editing enthusiast you wont notice the difference between 1333mhz and 2000mhz + ram,
This is down to the base clock lock.Its similar to older 33mhz base clock timing and locked or unlocked cpu's.
There you could get maybe 35mhz base but anything above that would make other components unstable.
My "old" lga775 pc , base cpu clock was the way to go with a locked cpu multiplier,still keeping pci at 100mhz but fsb and hence memory and cpu could be clocked up by varying cpu ref.
In my case 333mhz cpu ref became 500mhz which in turn became frontside bus speed of 2000mhz up from 1333mhz(x4),cpu speed of 4000mhz up from 2600mhz(x8 max)
and memspeed of 1000mhz(x2 min).
The 2000k sandybridge cpu's are like the closest thing to the celeron 300A (which would hold 500mhz,stock was 300mhz altho that was a fsb boost also),except this time its "approved" by intel.
I bought 8gb of 1333mhz ram for slightly more than the cost of 4gb of 1600mhz ram because for p67 ram speed isnt as impoertant and i needed more ram for a reduced swapfile size for my ssd.
Windows EI experience index is 7.7 for every component,which isnt bad . I am getting some lag on mouse input which isnt great for WoW but hopefully ill get it solved.
Check this
http://www.pureoverclock.com/review.php?id=1194&page=10My 2500k seems happy on autoclock of 4.8ghz even with a gx card overclock,they must have recieved a very poor chip.