Well, the thing is- I will probably get my 920 to 4.1Ghz+ with my WC set up. Even if I stick to 4.0Ghz, I am still beating Intel's current leading processor (965XE at 3.2Ghz and a whopping $1,000) by .8Ghz. I'd call that EPAC.
i7 920
1600MHz ram x2 = "3200/16=200" can use 200bclk max "21x200=4200mhz"
1866MHz ram x2 = "3732/16=233" can use 233bclk max "21x233= all the way up to 4893mhz"
As you see, if I use the Dominator RAM and get serious about my cooling, the limit is VERY high.